LEO Sayer is a little b*****d. Now, it’s easy to imagine what you’re thinking: that is a bit of a harsh statement. After all, we’re talking about the nice fella from West Sussex with the pasta twists hairstyle. We’re talking about the man who appeared on Top of the Pops back in 1974 singing The Show Must Go On and looking like Casper the Friendly Ghost after he'd been dressed that morning by his wee sister. And didn’t he have a voice that was close to miraculous?

And we still liked Leo after he took off the Pierrot costume and makeup because he sang some great songs such as The Dancer and One Man Band and Moonlighting. Although to be fair, when he switched musical track to go all disco with You Make Me Feel Like Dancing and sugary with When I Need You that tested us to the limit.

But we (sort of) forgave him because, well, he’s Leo Sayer, and he deserved it because he’d written terrific songs for Roger Daltrey such as Giving It All Away.

But in fact, it’s Leo Sayer himself, whose calling Leo Sayer a b*****d. Or rather it’s Gerard Hugh Sayer, the man he was before teaming up with manager Adam Faith in 1973 and storming the British charts with seven singles straight into the Top 10.

“I can’t be Leo Sayer all the time,” he explains, speaking from his home in a tiny village 65 miles south of Sydney, New South Wales. “He can be a little b*****d. And if I were Leo all the time, he’d want everything.”

He pauses. “That’s why I call myself Ge-rard,” he says of his real name, emphasising the second syllable, and making the name sound rather la-di-dah. “When I go to the airport, staff say, ‘Are you Leo Sayer’s brother?’ You see, everything I have, my bank statements, credit cards, the lot, have Gerard on them. Not Leo. It’s a good way to remind myself.”

The name check comes up because we’re talking about the effects of fame. Or rather surviving it. Leo Sayer is 69 in May but he’s fit and well. He emerges regularly from his Australian home to tour the world, and he's visiting Glasgow in May. Part of the reason Sayer has sung and danced his way through four decades is that he has managed to keep his curly head in check.

“I did cross the threshold a couple of times,” he admits of pop madness. “The first was in 1974, during the Pierrot time. I took another heartbeat change when You Make Me Feel Like Dancing hit America and I became a total icon there. Suddenly, I was walking on water and experienced the sort of adulation that Elton [John], Mick [Jagger] and David [Bowie] had.”

How did it manifest itself? “You find yourself asking to be driven around in a pink limo,” he says, “and if the limo turns up and it’s not pink you scream and throw a tantrum.” Did he actually do that? “Absolutely. What you think at the time is you can get from A to B in a Mini, or a Ford, but it’s so much nicer to get there in a Rolls.”

He laughs at his own folly. “A f****** pink one."

What about drink? Drugs?

“There were people who went for serious mind enhancement, like Jimi Hendrix or John Lennon, although I didn’t really need to do that. I was blessed with an incredibly fertile imagination. I had all my crazy ideas and they went into my songs."

That’s not to say he didn’t dabble. “Maybe I was helped because I didn’t start in the business too young. If you get into coke and LSD at 16 that could take a toll. I’ve smoked a few joints and popped a few pills over the years. I went on one LSD trip but I swore I’d never do that again.

“But during the quieter years in London it was time to go clubbing and try it out but it didn’t feel that special. And I didn’t want a heart attack. Plus, I bump into old rockers and they’re wheezy and tired because of the drugs.”

Sayer found his high on stage. “A lot of the people who got hung up on drugs had to deal with punishment of some sort. Like Michael Jackson and George Michael. There is a sad self-loathing thing going and in George’s case I’m sure it killed him. But that wasn’t me. I was happy when I became Leo Sayer.”

Growing up, little Gerry Sayer wasn’t happy being himself. A small, shy, dyslexic boy, he was bullied at school. He was clever and great at art but couldn’t tie his shoelaces until he was 21.

After attending art college he worked as a designer. Then gradually, after starting out as a harmonica player, he was coaxed on to the stage and began to sing in a band. As fate would have it, at one gig he met a songwriter called David Courtney, who declared he wanted to write with Sayer and introduced him to Faith, the former pop star.

“He was an ice-cream freezer, a geezer,” says Sayer, of Faith. “Waitresses would be in his bed in seconds. He was a lothario beyond comparison. I was a well-behaved boy when I met him, in fact I had just got married [to Janice, in 1973]. But when I told Adam my plans he said, ‘What are you doing, my son? You’re mad. You’re cutting down all your chances.’ But then the career started, this lifestyle with this crazy man running everything.”

Sayer reflects on the man who had a huge hit with What Do You Want (If You Don’t Want Money?). Faith “ripped off” Sayer to the point the manager earned way more than the performer and writer. (He later took Faith to court to recover some of the cash in the 1990s, winning back £650,000.)

Perhaps astonishingly, Sayer is sanguine. “I don’t really blame him. If I had some guy called Leo who was not that aware of how the world worked I’d have done the same thing. And I can’t hate the guy, even though he ripped me off rotten because he put me there. His confidence in me was the cloak that I wore.

“He’d say, ‘Here’s the cloak, go on my son!’ and I’d put it on. He was a role model. Some people called him my svengali but he never commanded me or threatened – it was always encouraging. He had a feeling about me. He knew who Leo Sayer could be and he was dead right.”

He adds, laughing: “And I’m no longer a very shy chap – not any more. I have developed his chutzpah and I can chat up women as well. He handed over nearly all of his gifts to me.”

Faith brought the business connections and the cloak, but it was Sayer who came up with the Pierrot costume. “In those days we were all looking for an original look and we were inspired by people like Alex Harvey and Elton and Ziggy Stardust. The idea came from a movie I loved when I was at art school, Les Enfants du Paradis. Jean-Louis Barrault played Pierrot, an actor who never came out of costume.”

The get-up helped him become Leo. “It was transforming. Out of the corners of your eye you could see the white makeup and this was a suit of armour. I became an actor and played at being Leo Sayer. The look imbued the confidence. Yet while this was my construction the guy telling me I could carry it off was Adam.”

The costume wouldn’t have worked without a clutch of great songs. The hits kept coming. “David had the knack of melodies and I had the lyrics, the ideas, so we never felt it would run out.”

They wrote most of Daltrey’s first solo album. “Adam would say ‘Keep writing, lads. I’ll deal with the other stuff.’ And we challenged ourselves, fantastically. Every song was different. Long Tall Glasses was nothing like The Show Must Go On. We tried to explore, to be edgy. We tried to follow in the footsteps of the Beatles.”

Sayer gained some very high-profile fans, including Paul McCartney, who early on told him to keep his long, curly hair. But there was an even bigger fan in the background, who Sayer didn’t learn of until he fell off stage and cracked his knee.

“It was in Alpine Valley, Wisconsin, in 1977,” he recalls of the outdoor stage built high on a platform. “I leaned against a rail talking to someone and fell 27 feet and landed on my leg.

“I was in and out of hospital for months. But the show did go on.” Until he got to Memphis. “I was in the dressing room and my knee went and I crawled into a ball and couldn’t get up. I was carried off by a big security guy called Michael who’d once played for the Miami Dolphins and I heard he had an important boss.

“He didn’t tell me who his boss was but the next day his boss called me. It was Elvis Presley. He came on the phone singing You Make Me Feel Like Dancing, down the line. ‘I love that song, man.’ Then Elvis said, ‘Michael has been looking after you. I hear you’re a great guy. And you need to come over to the house.’ I was stunned, and got ready to go to spend a few days with Elvis and his girlfriend Ginger. But the next morning I heard on the radio Elvis had been taken to hospital and died.

“Years later, I began to think I must have dreamt the whole thing. But I met Ginger at a dinner in London, and she said ‘Elvis had been so excited at the idea of spending a few days with you.’ I had tears in my eyes when she said that.”

Sayer is a survivor in the business, perhaps because he lives in a quiet corner of Australia, in a lovely house with his ex-partner and business manager Donatella and with a garden full of fir trees and parrots.

“It’s very easy to live here,” he enthuses. “All the creature comforts and lots of space. You can’t get away from the right-wing politics but that’s the same all over the world. But I do miss M&S sandwiches.”

He’s certainly aware the pop world doesn’t aid longevity. “I feel like the last man standing,” he says, talking of the deaths of the likes of Bowie. “I remember showing Prince around Warners' recording studios. He was the nicest kid. But thankfully there are still some older performers out there, such as Boz Scaggs and the Stones. And Rod’s still going and looking great.”

Sayer has managed to keep a career going although there have struggles along the way, especially during the 1980s. “I was available for weddings, funerals, bar mitzvahs, I’d do anything and a lot of it would not be career-enhancing stuff.”

You’d like to think John Lennon wouldn’t have gone into Big Brother but then Lennon hadn’t suffered the same financial losses as Sayer, who made the headlines 10 years ago when he stormed out claiming the producers wouldn’t give him fresh underwear. But look at the YouTube video and he actually comes across as someone rebelling against the loss of his dignity.

“They had been taking the piss,” he says of the show’s producers. "Enough was enough.”

He continues to tour and make albums in his studio at home. “I’m still driven. I feel I still haven’t made a great record, like Neil Young or Bob Dylan.” But he has the best of worlds, the Gemini who can switch from Gerard to Leo when the moment calls for it.

“Sometimes I feel like Leonard Cohen when he went off to become a Buddhist,” he says. “It may not be fame but I think it’s success. It’s not what Elton or Mick has but I guard it with my life.”

Perhaps Elton should check in at airports as Reg? “He should,” says Sayer, laughing. “The last time I saw him he was really unhappy. I said, ‘Have you ever thought of going back to being Reg?’ and he smiled and said, ‘Every day.’

"He said to me, ‘You’re really lucky you can go back to being Gerard.’ And he’s so right because Leo can be a b*****d.”

Leo Sayer plays the Pavilion Theatre, Glasgow, on May 5.