Judi Dench has called for Camden Council to reconsider its ban on advertising boards outside the drama school where she was a student.

The Royal Central School of Speech and Drama in Swiss Cottage receives up to £150,000 from advertisers using two hoardings outside the school, which it then donates to youth projects in Camden.

Camden Council has banned the boards, which have been in place for 27 years, because they do not have planning permission.

In an open letter to the council, Oscar-winning Dame Judi said penalising the school’s “good will” was “misguided” and that the hoardings brought “considerable benefits” to arts education.

Advertising revenue of £50,000 helps fund the annual Shakespeare Schools Festival, which works with 1,000 schools across the UK to put on half hour Shakespeare adaptations in local theatres.

Cllr Valerie Leach, Camden’s cabinet minister for regeneration and growth, said that the council had a duty “to protect local areas from hoardings without any formal planning permission, such as this site”.

The school is one of the most prestigious drama academies in the UK.

Its alumni include Sir Laurence Olivier, Sir Cameron Mackintosh, Harold Pinter and Jennifer Saunders.