Saucy images are said to litter the Huntley and Palmer biscuit tin

The Huntley and Palmer tin, made in the 1970s at the company's Liverpool factory, appears on first glance to show an idyllic lunchtime scene.

On closer inspection, the illusion of tranquillity is shattered by drawings in the background of a naked couple.

These are said to have been added by a designer who had just been sacked.

The tin sold for £119 at Bonhams Auction House in Bath on Monday.

Amid the scenes of ladies and children lunching around a table at a Manor House, are said to be those of a man and woman locked in an amorous embrace in a flower bed.

The tin also depicts two dogs mating behind a tree and a jam jar decorated with an obscene label.

The tins have become widely known as the 'Disgruntled Employee Biscuit Tin', a very apt name for them indeed.

Patrick Toynbee, Bonhams Auction House

The late additions to the piece were only spotted after the biscuit tins had been produced and sold around the country.

Patrick Toynbee of Bonhams said: "Huntley and Palmer are famous for their decorative biscuit tins which adorned British tea tables for almost a century.

"However, there is also a well-known story passed on amongst collectors that when one of their employees received notice of being fired, he decided to decorate some of the tins in a manner which would make his displeasure with his employers very clear, not just to them but also to their customers."

But Mr Toynbee goes on to say the added saucy images are "not clearly visible".

"Obviously the company wasn't even aware of them and the first they heard of it was when a grocer alerted them.

"Since then the tins have become widely known as the 'Disgruntled Employee Biscuit Tin', a very apt name for them indeed," he said.