Harry Shearer, who was bassist Derek Smalls in the classic film, said that the plan was to make people think Spinal Tap were a real band.

And sure enough, Gallagher stormed out of a Spinal Tap gig after brother Noel broke the news that they weren't real.

There is a lot of Tap activity this month with the release of a three-DVD and blu-Ray version of This is Spinal Tap along with the DVD Unwigged and Unplugged: An Evening With Christopher Guest, Michael McKean and Harry Shearer.

In June, Spinal Tap appeared at the Glastonbury Festival to promote their Back From The Dead CD.

"I was kind of expecting lots of mud and people messing about in it, but it didn't happen. It must be the curse of Spinal Tap," Harry said. "I had read about Glastonbury and thought that there would be a lot of mud."

The 65-year-old added: "This Is Spinal Tap has leaped generations, but I never imagined it would sustain the longevity that it has done.

"I have had kids in bands come up to me and say they learned what not to do at gigs or on tour from watching it."

A quarter of a century on, Harry, together with fellow Jewish actor Christopher Guest (Nigel Tufnel) and Michael McKean (Dave St Hubbins), are still packing out venues all over the world as Spinal Tap.

As well as Glastonbury, they played Wembley Arena three days later on the One Night Only World Tour.

They opened the show as The Folksmen, another spoof band who made their first appearance in Guest's 2003 mockumentary A Mighty Wind.

Harry added: "I think some people, who didn't know who we were supposed to be, were mystified.

"They were just there for Spinal Tap and there is nothing worse than getting a frosty reception, although most people recognised us."

As Harry and Guest are Jewish, would they consider dressing up as klezmer band and playing eastern European Jewish music?

Harry retorted: "There are some wonderful klezmer bands, but that kind of music is not too well known among the general public.

"I know a lot of klezmer bands and they are brilliant musicians. I really like the Klezmatics, for example."

As well as The Folksmen and Spinal Tap, the trio recently completed a 28-date tour of America performing music from the two bands, which forms Unwigged and Unplugged.

Harry - who is in the UK as his wife, Welsh singer-songwriter Judith Owen, is on tour with comedienne Ruby Wax - explained: "I thought it was an interesting challenge for us and how we would treat the songs.

"We had a lot of fun doing it and we would love to bring it to the UK. I guess the idea for bringing out the DVD here is to whip up an uncontrollable ground swell among our fans in Britain."

But Harry's talents don't just lie in music and film.

He has been the voice of many of The Simpsons characters since its inception including Montgomery Burns, Ned Flanders and Kent Brockman.

"Nobody in their right mind would have thought it would become as big as it has," he admitted. "Matt Groening, the show's creator, was a fan of my work and I enjoyed his newspaper column.

"He called me to ask if I could voice some characters and I just said 'I don't think so'. There was a lot of arm-twisting and I was persuaded to do it.

"We were on the Fox network and that was a fledgling channel at the time and we just thought it would be a nice six-week gig. It turned out to be a global hit."

Harry, whose favourite character is tyrannical Springfield businessman Mr Burns, said the cast does have fun on the set, but not as much as one would think.

He continued: "We do sometimes crack up, but what I have found is that actors on the sets of dark medical dramas have much more fun - that is ironic.

"I guess in comedy it is all about the business and getting it just right."

Brought up in Los Angeles, the son of Austrian-born Mack and Polish-born Dora, Harry was a talented pianist and his teacher/agent landed him a part on The Jack Benny Show.

It was there that he was taken under the wing of legendary impressionist Mel Blanc, who voiced the likes of cartoon characters Bugs Bunny, Daffy Duck, Sylvester the Cat and Wile E Coyote.

Harry recalled: "Mel had a son the same age as me and, as my dad had died young, he was really paternal towards me. He was a great man."

Harry made his first film appearance in Abbott and Costello Go to Mars and later was cast in the Biblical epic The Robe.

He went on to study political science at the University of California and then worked at a high school, teaching English and social studies.

He first met Michael McKean when they were both part of a radio comedy group in the 1970s called The Credibility Gap.

Harry, who names Peter Sellers, Peter Cook and Dudley Moore as his comedy heroes, thought he had reached his Promised Land when he landed a job on the cast - and as a writer - on the legendary American show Saturday Night Live.

But the series that produced the likes of Dan Aykroyd, Chevy Chase and Mike Myers ended in misery for him.

Harry recalled: "I would describe it as like taking a salary in a suburb of hell. I will never forget the ultra competitiveness of the place.

"The emphasis in comedy should be on collaboration, but it was never like that.

"I didn't like the fact that you had to be trembling with fear when you're trying to be funny - it was silly, but endemic of the place."

His hell turned to heaven with This is Spinal Tap in 1984, which he co-created and co-wrote - and Harry never looked back.

He has appeared in a number of improvised films, including Waiting For Guffman, A Mighty Wind and For Your Consideration, which told the story of a group of actors making a film called Home for Purim.

Harry said: "Improvisation comes to me, but only after a great wave of fear has taken me over. I remember filming For Your Consideration and I was speaking to the other actors on set and they told me they had experienced nerves too.

"The good thing about improv is that there are no expectations and you can relax, you can take it where you want it to go within reason."

He was surrounded by music, of the classical kind when he was younger, as dad Mack studied it in his native Vienna.

Harry recalled: "It was always played in our house and my parents used to take me to the opera. I guess that is what turned me against opera.

"It is funny because my wife grew up around opera and her father was in the Covent Garden Operatic Choir and she just adores it."

Later musical influences included Frank Sinatra, Ella Fitzgerald and The Beatles. Harry said: "The Beatles changed everything for me - they were 'it'.

"I remember doing a gig with Spinal Tap at the Royal Albert Hall in 1992 and we quickly ran off stage to do a costume change and there was a solitary figure at the side who gave me a thumbs-up. It was George Harrison. It was unbelievable.

"Earlier this year we were rehearsing for the Unwigged tour in the San Fernando Valley.

"We had hired a big rehearsal space and were just setting up when Sir Paul McCartney walked in. He was like, 'hi fellas, give us a few tunes then' and we were all completely lost for words.

"But we did a couple of songs and he liked them. He is a lovely man."

As well as a home in LA, Harry and Judith also reside in New Orleans and he has been publicly vociferous in his anger at what he says is way the media lied about certain events surrounding Hurricane Katrina, which battered the city four years ago.

"How the government went about themselves afterwards was a catastrophic failure, there was such a lack of urgency," he explained.

And, although he is pleased that the Bush administration has gone, he remains cynical about Barack Obama.

Harry said: "I am a registered sceptic. Emotionally, I thought the election of Obama was a great moment for America. That other scurrilous bunch had to be tossed out. But I have been disappointed by the new government in the last six months. Why are we still in Iraq, for example?

"We are acting like an empire and then we tell people, 'no we are different to other countries in the way that we behave'.

"Oh really? Let me think about that. Slavery, check; treating the Native Americans in the way we did, oh yeah. Realistically, we are not different."

Although Harry was brought up to celebrate the high holy days, he said he is no longer religious and doesn't believe being Jewish has had an effect on his work.

He added: "I look at people like Philip Roth and Woody Allen with interest. Most of their stuff is coloured by Judaism.

"My experience was not like that. It was coloured by growing up in the salient, showbusiness world of LA."

Harry doesn't have any film projects in the pipeline, but revealed that he is waiting for Guest to come up some ideas.

However, he will not appear in nor watch any films which contain violent scenes.

Harry explained: "I just don't like them and I won't do them. It is funny because my wife has the most vivid and lurid nightmares and my nightmares usually consist of me going to the post office and finding out that they have run out of stamps.

"She asked me if I had seen the Coen brothers' film No Country For Old Men, for example, but I hadn't because there was violence in it."

Harry is showing now signs of slowing down.

He said: "I am 65, but I am in good shape."