At the Masonic Hall in Bristol, where portraits of past masters of the lodge stare across cold marble floors, a group of middle-aged men are putting on brightly coloured jackets and combing their wigs.

As they tune their guitars, they joke about this slightly surreal venue and the sign that says no regalia to be worn in the bar. In the ballroom just down the hall, a birthday party is in full swing, and the band is the surprise act. As soon as coffee and speeches are over, they take the stage to whoops of laughter and applause.

“This is a Masonic lodge - could you please behave with some decorum,” says singer Martin Dimery in his best Liverpudlian accent, as he takes the microphone. Then they launch into “Please Please Me” and guests in dinner jackets and party frocks get up to dance.

Some people perform in tribute bands for a living. But for media studies teachers Martin Dimery and John Freeman, getting up on stage and pretending to be John Lennon and Paul McCartney is a way to let off steam on a Friday night. And they’re rather good. Their five-piece Sgt Pepper’s Only Dart Board Band (they’ve got Sgt Pepper supporting on keyboards) recreates an authentic sound, delivering hits such as “Penny Lane”, “Hello Goodbye” and “We Can Work It Out”. They play it for laughs. “We are the only Beatles tribute band older than the originals,” they tell the audience. “We used to be on LSD - now we’re on Viagra.”

Martin Dimery (John) and John Freeman (Paul), met when they were both teaching at Frome College, Somerset. Mr Dimery has since moved on, and now teaches at top independent school Millfield. Mr Freeman, 47, formerly played bass in R ‘n’ B band the Havana Fireflies, and has written music for stage and TV. Mr Dimery, 45, once acted with the National Youth Theatre, and has taught drama and written stage plays and musicals.

They formed their tribute band seven years ago for a stage show, All You Need is Love, and carried on with backing musicians Stuart Berry (Ringo), Lester Mason (George) and Rob Waller (Sgt Pepper). They have played throughout the UK, including the Philharmonic Hall in the Beatles’ home city of Liverpool, and have appeared as a support band for Jools Holland. Mr Dimery has written a book about the band’s exploits, Being John Lennon: days in the life of Sgt Pepper’s Only Dart Board Band. The band spent part of the summer holidays on a near-disastrous tour of the Czech Republic, when rain and the flooded Vlatava river left some venues 10 feet under water. And their tour bus was broken into - a couple of Beatles wigs were stolen.

How does being in a band and teaching media studies relate? Martin Dimery says:“One of my areas is the social effects of popular music, although I’m like lots of us our age - I’m a bit linked to the past. My era’s been and gone, really. But it’s interesting how many pupils still listen to and love the Beatles. I was self-conscious about doing this when I moved to Millfield. You get a stereotypical view of what a school would and wouldn’t approve of. But they have always been very supportive.”

John Freeman believes their out-of-school talents disprove the tired adage:

“Those who can, doI”. “In the teaching profession, there are many talented people with lots of other skills. We used to say at Frome College that you could get almost anything you want done by a member of staff. We had electricians and people who could mend your washing machine, as well as musicians, writers and artists.”

What do they get from being in the band? “It’s the social aspect,” says Mr Freeman. “It’s an excuse to come out, have a couple of pints, spend some time with the chaps and play some music.”

But what do their students think? Is it cool for two middle-aged teachers to be seen dressing up as Sixties pop idols? John Freeman and Martin Dimery insist they keep day job and band separate. “Occasionally, I’ll put up a poster if I’m doing something local,” says John. “But a lot of people don’t even know that I play. A lot of kids don’t know. It’s all in the disguise. That’s the good thing. You can play a crap gig, and as soon as you’ve taken your wig and coat off, no one knows it was you.”

Being John Lennon: days in the life of Sgt Pepper’s Only Dart Board Band by Martin Dimery is available from SAF Publishing pound;9.99. Order from www.safpublishing.com, tel: 020 7836 1151 or fax: 0207 240 9880