The delicate job of cleaning a magnificent piece of artwork by Clangers creator Oliver Postgate has revealed another painting which had remained unseen for decades.

It was discovered at the University of Kent where the work by the late creator of some of television's best-loved children's characters has hung in the grand hall of Eliot College since 1992.

The piece, A Canterbury Chronicle, was commissioned by then Master of the College, Shirley Barlow, following a donation from Major Stanley Holland, a long-time friend and benefactor of the college, for a new art work.

But as it was being cleaned recently, the two outside sections were found to fold inwards like doors to cover the main piece and on them was discovered another painting.

It shows Thomas Beckett and Henry II whose alleged remark "who will rid me of this turbulent priest", is said to have led to the murder of the Archbishop.

In the bottom right hand corner is a cartouche of two mice holding a scroll confirming the work to be by Oliver Postage and dated 1992.

The current Master of Eliot College, Stephen Burke said: "I was delighted to see what was unveiled and it was a huge surprise after all these years.

"The college is honoured to have such a great piece of work by Oliver Postgate, who lived and worked locally.

"I would also like to acknowledge the kind generosity of Major Holland who made this possible.”

Back in 1992, Mr Postgate said it was the largest scale mural he would undertake as it featured around 300 characters - most "up to no good".

But he clearly thought some students were up to no good too, complaining in a memoir at the time that he was not impressed by "roistering students" flicking spoonfuls of brandy butter on his newly-hung work and damaging the paintwork.

Working with Peter Firmin from a small studio in Blean, Oliver Postgate helped create The Clangers, Ivor the Engine, Noggin the Nog and Bagpuss, which was voted the most popular children's television in a 1999 BBC poll.

He died at a nursing home in Broadstairs in 2008, aged 83, and after his death there was huge recognition of his influence and effect on British culture, and affection for the role his work had played in many people's lives.