John McKenzie, who survived by eating a few chocolate coins and some biscuits he had bought for his great nieces, said: "It was only two days."

Mr McKenzie's ordeal began when he called at the Ribblesdale House medical centre in Bury, Greater Manchester to collect a prescription for tablets for a heart condition.

Instead of taking the lift to the first floor he travelled to the second and emerged into darkened, empty offices.

An hour later staff locked up the building for the weekend and went home.

"Nobody can have heard him banging," said practice manager Joan Richardson. "We are very sorry this happened."

Massive search

Outside, a massive search involving tracker dogs and a helicopter was being carried out by police alerted by his frantic family.

The pensioner was freed after almost 48 hours when district nurses arrived for work on Monday morning.

But Mr McKenzie, a retired builder, kept silent about his ordeal and staff assumed he had just arrived in the building.

It was only when he arrived home safe and well that the story of his lost weekend emerged.

Mr McKenzie says he's none the worse for his ordeal.