For many Britons over the age of forty, the expression "What the Butler Saw" will awaken distant memories of seaside holidays and penny arcades at the end of the pier. It is the common name for a machine known as a 'mutoscope'; a contraption introduced at the end of the 19th century which allowed 'moving picture' sequences to be viewed by an individual through a 'peephole'.

The introduction of the "What the Butler Saw" machine coincides roughly with the development of photography, but before the development of the cinematographic projector. The machine consisted of a rolodex-type drum, upon which were fixed a number of cards with photographic images on them. Viewing the the sequence of cards in quick succession gives the impression of movement, just like a 'flick book'.

"What the Butler Saw" machines were constructed from cast iron, and often had a coin slot on the side. After depositing the required amount, the viewer would look into the viewfinder and crank a small handle on the side of the machine to animate the scene inside.

"What the Butler Saw" became synonymous with the mutoscope very quickly as the machines were quickly surpassed by the burgeoning phenomenon that was cinema - the machines were relegated to offering cheap titillation in seaside arcades, where, for a penny, you could witness "what the butler saw" - typically a rather tame, 'through the keyhole' peek at the lady of the house getting undressed or bathing, blissfully unaware that she had an audience.

The public life of these coin-operated machines' came to an abrupt end in Britain with decimalisation, in 1971. Now, just the like the butler himself, the "what the butler saw" machine is, for the most part, just a tiny part of the British collective identity.

Harmless entertainment or a training aid for seedy voyeurs? The decision is yours.