Mr and Mrs Neil Diamond look strangely similar even though he is 71 and she is 42. The same eyes, the same slightly wary nature, sensitive and warm. And when they smile they smile with their whole face.

Katie has an obvious kindness about her. She looks after him both as a manager and as a wife. They met when she was working for the management company to whom he had recently signed. It was not love at first sight, it was business, until gradually she wove her way into his heart. They got married earlier this year.

He too has an almost puppy like desire to please her. Both of them seem to carry a kind of emotional weight.

He has spoken before about his life as a solitary journey – how he was lost in the creative process.

Diamond talks with his slow gravelly voice, it’s almost a purr. He’s talked before about being a loner, about how his past relationships have suffered because he was driven by his music and his songwriting.

With time and maybe love he’s realised he doesn’t have to enjoy only solitude and that he likes people as well. ‘There was no eureka moment where I went hey, I’m going to be with people and have fun. It was a gradual growing up, a gradual self-awareness. I always liked having fun with audiences.’

We are seated in a badly lit New York hotel room. Katie takes charge of pouring decaffeinated coffee. They seem extremely comfortable together. They met a year or so after he ended his long-term relationship with Australian production assistant Rae Farley. He met Farley the year after his divorce from his 25-year marriage to Marcia Murphey who he married the year he divorced his first wife, high school sweetheart Jaye Posner.

He felt a lot of guilt about the failure of his 25-year-old marriage. So much so that he didn’t bother to correct rumours that said he paid his wife $150 million, said to be the highest recorded alimony settlement at the time.

‘It wasn’t true,’ he says as he casts his eyes to the floor. He claims that newspapers simply made up the sum and he didn’t bother to correct it. Even his wife asked him about it. Was she happy with the settlement she did get? ‘She was. She got enough to live on for the rest of her life.’ Was he so generous because he felt such guilt? ‘Somewhat.’ He almost winces. ‘It’s true. I did feel bad.

‘I don’t have many feelings about my divorce  now because we’ve been divorced for 20 years. I do have some feelings of guilt about my life. Guilty that I wasn’t with my kids more because I was travelling. But I’ve spoken to all of them a number of times about it. They all have good memories of growing up and I loved them completely when I was back in town. I was theirs full-time.’

Maybe it makes it more special and intense to have a father that works on the road. Maybe if you’d been around all the time there would have been more bickering?

‘That’s right,’ his eyes lighting. ‘I have never bickered with my kids. I was always happy to see them and they were always happy to see me. And I think they still are.’

He has had a lifelong relationship with guilt. ‘I see a therapist. She is very useful. I learned to express myself and I learned about myself with the help of a psychologist. She didn’t make me a better songwriter but she made me an easier person for me to live with. She had nothing to do with my songs – that’s a solo effort. She’s made my life a lot easier because I understand things a bit better, because I’m not torturing myself.

‘I used to blame myself for everything. I have moderated my feelings over the years. Guilt and achievement and responsibility, all of these things…’

You felt guilty for achieving? ‘No. Achievement is one of the things you have to deal with. Your self-achievement, your self-image. I never felt guilty for achieving anything because I always worked for it. but sometimes I feel I am worthless, useless. What am I here for, what am I doing?’

Does he still feel like that? ‘Sometimes. And somehow you have to deal with it. My psychologist has been very helpful in opening the doors to my mind and help me understand myself and the reality of life. I see her once a week, face to face. Occasionally I’ll call her on the phone if I’m out of town. But it’s almost always face to face and I have been doing it for ten years.’

There must have been an instant knowingness when he and Katie first met. ‘No, there was nothing. She was just another business person handing me work to do and another business person I was trying to get away from. I stopped trying to get away after a year or so, once I got to know the person she was, and I liked that person very much. Katie’s got a big heart and she’s very transparent. I can read her heart from a mile away. She does a terrific English accent which makes me laugh every time she does it. Katie, remember where we were staying last time we were in London, darling?’

‘Dawchester,’ says Katie, in a very strange cockney posh. But it’s a valiant attempt. Did it take Katie a year for him to weave his way into her heart? ‘No, she loved me immediately,’ he laughs, a very low naughty laugh.

Katie says, very politely, ‘I took my work very seriously. And when we first started working together it was work on both sides. I wanted to work with him. He was one of the biggest iconic singer songwriters of all time and as a manager I was thrilled to have him as a client. We worked very closely for that first year because he was on tour and we spent a lot of time together. When we first met neither of us were interested in each other. He was work as far as I was concerned.’

They were both single and available? They both nod. I wonder if he’d resigned himself to being alone for the rest of his life after his two marriages and long-term relationship had fallen apart.

‘No, I had not resigned myself to being single, but I wasn’t looking. I was busy doing my work and Katie appeared. It was totally unplanned and unexpected.’

How does he make sure that their relationship keeps working? In the past he’s said that music was his main mistress. Music demands from him emotions that are intense. His second marriage is said to have failed because he didn’t have enough time emotionally or physically left over for his family.

Is it complicated working together having a business relationship as well as a romantic one? ‘We are still working on that because there are times where the work will interfere with our personal relationship. There are times I want to talk about something and we might be in the middle of having breakfast together. I’ll want to talk about something coming up and Katie doesn’t want to talk about that. She wants to do the crossword puzzle and have breakfast, so she’ll say “Can we talk about this later or can we set up a meeting to talk about it?” And I have to say, OK. We’ll talk about it another time.

‘We’re still in the process of working this all out. It requires some give and take on both our parts. I respect her a lot. She’s a professional. She’s very experienced. She knows the business and that allows me to not be drawn into the business part so much. It allows the creative part of me time to blossom, time for me to write songs, time for me to do what I do best.’

Does he write songs more easily when he’s happy in love or more miserable? ‘Misery has never been a productive stimulus. I’d rather be in a good frame of mind because then you’re energetic, you’re outgoing. Although I have written some of my best songs when I’ve been down and not particularly happy.

‘I get unhappy if I get stuck on a song, if I can’t get a line that is satisfactory to me or if I’m working on an idea all day and it’s not working out. That can really preoccupy and distract me. If one of my kids is sick I’m unhappy. If I get a cold I’m unhappy. If I’m underworked I’m unhappy. If I’m overworked I’m unhappy.’

He says all of this with a sense of irony. Most of that severe unhappiness seems to be in the past. He actually strikes me as a very happy man.

Diamond’s many moods from dark to exuberant, can be found on his just released The Very Best Of Neil Diamond featuring all beloved classics like Solitary Man, Sweet Caroline, Beautiful Noise, Hello Again, and You Don’t Bring Me Flowers, the duet with Barbra Streisand. He is working on songs for a new album and that is going well.

‘I’m happy because I’m occupied with something that I love doing. Keeping busy is the most important element of me being happy and of course having a wonderful wife makes me happy, to know that I don’t have to go through my life and bear it alone. That’s a happy thought for me. I have someone to talk to about it.’

Was he lonely when he met Katie? ‘I think I was probably lonely. I don’t like to be alone. I’d much rather be in a loving relationship with a woman any day than being alone.’

Did his last long-term relationship (with Rae Farley) end unhappily? ‘I’d say it did end unhappily. It wasn’t a serious relationship. It was going nowhere. There were no marriage plans. It was difficult. It lasted too long.’

Did it last too long because it’s hard to end things even though it’s hard to be in them? ‘I think so,’ he nods earnestly, still troubled by the thought of it.

On stage he has always been a flamboyant performer, over the top, fantastical gyrations that would seem impossible for a man of his age who today walks a little stiffly and places himself in a hard backed chair. He’s wearing dark jeans and a dark sweater, his face craggy and hair more salt than pepper, but he’s extremely magnetic. His eyes draw you in to their suffering and his need to connect.  He has over 60,000 followers on Twitter and he follows no one.

‘I believe I am allowed to be over the top on stage and I enjoy that part of myself. Tweeting is expressive, I wouldn’t say therapeutic, I wouldn’t put it that deeply, but I like to share what I’m thinking. Here’s a picture of my dog. It’s funny.’

The Diamonds live in LA where they love walking their dogs Poker and Shamrock and Katie likes to ride horses and spend time with her rescued cat Brigitte. Diamond is particularly close to the dog he calls Pokey who he rescued from being put to sleep. They never buy animals, only ever rescue them.

‘There was something about his eyes that got to me. He was a funny looking guy (part spaniel part something else). I looked at him and he looked at me back. There was a little bit of communication. So I asked this person who was in charge of adoption do you mind if I take this dog for a walk so I can get to know him and see if we like each other. He said sure, so I took a leash and Pokey and I went for a walk and we had a heart to heart. I asked him how he was doing and where he lived before. He was a grown-up dog, mature, and he said, “I don’t want to talk about that right now” so we talked about life and he was enjoying the smells. This is all mentally. And we got to know each other and I got to like him. I think he got to like me. So I said I’m going to take this dog home because I think we can get along and I did just that. The guy in charge of the adoptions was called Chance so that’s why I called him Poker.

‘He’s a great dog and we’re great pals. I talk to him all the time. Don’t people usually talk to their animals? Our conversations are quite abbreviated. We haven’t discussed the Bible yet or the meaning of life, but we have discussed, “No Pokey it’s not a good idea to jump on the couch right now.” And he goes, “Oh okay.” He’s a very reasonable dog. That’s one of the things I appreciate about him.’

Shamrock was a golden retriever puppy who Katie fell in love with when she ran into him at a farm where she rides horses. ‘He’s a very affectionate dog and somehow you have to put a little control over his affections. He will climb up on your lap and sit there, but he is as big as a person.’

Possibly Shamrock is Katie and Pokie is Diamond. ‘That’s exactly right,’ he says. I’m wondering was Shamrock the first significant present he gave Katie and was this the gift that established their relationship? ‘I was her first big present. I’m not taking second place.’

When you decide to get a dog with someone it’s making a statement that you are getting domestic, that you are moving in a permanent direction.

‘Yes, I’ve heard that but I never thought that. I have given puppies as presents before because I love dogs and I thought it would be nice. Katie wanted Shamrock. ‘

Katie was at a friend’s farm where she rides horses and she discovered one of their dogs had puppies. She fell in love with Shamrock, a golden retriever puppy.

‘I didn’t really want another dog, I thought Poker was just fine. But Katie’s got a big heart so I grudgingly in a way said alright, Shamrock it is. And he turns out to be a good guy.’

He is quite a contradiction. On the one hand he loves to make people laugh and loves nothing better than to charm an audience. He is warm, easy to connect with, yet he has spent most of his life in his own head, even if he was in a relationship. His best friend is the one he met at high school who is waiting downstairs to have lunch with him.

He met Herb Cohen when he was 17 and Herb was the captain of the high school fencing team. They had an instant connection and Diamond joined the team. ‘He was the best, I was the worst. But scouts offering scholarships for college came to look at Herb, so they took me as well. We went to NYU together.’

He once said that he didn’t make friends like normal people. ‘I do have other friends. I made a point of opening myself up and allowing myself to make friends. Before that all I had was my work, my family and that was it. The only people I had contact with were the people that work for me and my kids. I’m in touch with my kids all the time.’

I imagine there was an unfathomable void in his life when his 25 year marriage disintegrated. Is he in touch with his ex-wives? ‘I am but not on a regular basis. When it is called for. When it is necessary. To talk about the kids. Sometimes to talk about other things.’

‘My first wife was Jewish. My second wife was not Jewish. My third wife is Catholic. There will not be a fourth wife by the way. I’ve been warned by Katie.’

I ask Katie what exactly did she do to warn him? She blushes. ‘I haven’t warned him anything.’ He interrupts. ‘She hasn’t. I just don’t want ever to lose her. She is too fantastic.’

What is being in love like for him? ‘Being in love completes the perfection of my life. If there was anything missing in the last 20 years it was that I was not in love with anybody and I am in love with Katie. I am in love and I love her.’

I ask Katie is she in love? ‘Absolutely.’

Does she think that’s different to loving somebody? ‘Yes, I do. And I both love him and am in love with him. I love him with all my heart.’ They look at each other. Their eyes lock. You believe them’.

The Very Best of Neil Diamond’ is Out Now