By Barbara Lewis

LONDON, May 19 (Reuters) Beyond the bright lights of London's West End, small, independent theatres, tucked away in tiny makeshift spaces, provide an arena for young actors to make their mark.

But these venues, hidden in the backrooms of pubs, former warehouses and disused churches, are also a platform for some of the capital's oldest acting talent.

Gabrielle Hamilton, who will be 83 in June, belies the popular conception that all the best female roles go to the young. She has just won rave reviews for her performances at Theatre 503, a homely South London pub theatre lauded as one of Britain's most important centres for new writing.

Fresh, feisty and charming despite an emotionally draining two-week run, she's now eager to find her next part.

''I never want to retire. It's so interesting working in theatre. There's nothing as interesting as doing that. You can like lots of other things, but it's not the same,'' she said.

While elderly actors are not so uncommon on television or in film, they are a rarity in the unforgiving setting of theatre and especially small-scale theatre, where the acting comes under the spotlight and there is no time for retakes.

Hamilton relishes the challenge.

''Small spaces are lovely. You get a wonderful sense of what the audience is feeling,'' she said.

''It's lovely to work with young people. They're usually very good and interesting and they're very nice to old ladies.'' FROM REPERTORY TO SMALL-SCALE London's small-scale theatres are often referred to as fringe, although their advocates prefer the term independent because they feel ''fringe'' can imply amateur.

They have taken on the role that Britain's repertory theatres performed in Hamilton's youth.

With tight rehearsal schedules, limited budgets and short production runs, just like in today's independent theatres, repertory allowed actors to build experience in the provinces before transferring to the West End.

''We did a play every week. We had to work very quickly. You had to learn things very quickly. There were sometimes things that you had to cover up or deal with. Michael Caine had a phrase for that 'embrace the difficulty','' Hamilton said.

''The repertory theatres were all over the country. It was a wonderful time because you had such a variety of parts to play.'' Hamilton developed her love of drama from childhood dancing classes and then amateur dramatics while she served in the Women's Auxiliary Air Force during World War Two. She later graduated from London's Central School of Speech and Drama before embarking on repertory.

After the advent of television, many repertory theatres closed and Hamilton herself was drawn to the new medium, starring in many of the classic literary adaptations for which the BBC is well-known, as well as in popular soaps.

Her latest role in Theatre 503 -- described by London's Guardian newspaper as ''arguably the most important theatre in Britain today'' because of the wealth of new writing it has staged -- was in ''The Ash Boy''.

Written by London-based Irish writer Chris Lee, the drama about mental illness and old age would be harrowing but for its offbeat humour, poetic language and sublime acting.

Hamilton played the aged but sprightly and sharp-as-nails mother of a mentally disturbed son. The writer insisted she should have an Irish accent, so she set about acquiring one.

''I had to have a Dublin accent. I recorded people speaking Dublin and I did it,'' she said.

The result impressed her colleagues, as well as the critics.

''What is real and immediate is the vitality in one so experienced and advanced in years,'' said director Gene David Kirk.

''It makes me want to say to some of the younger generation: just get out there and start doing it, then it will happen. It will not drop in your lap. Doing it is what Gabrielle has done and does and she just keeps on doing it.'' Reuters SRS RS0848