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The Admiralty Landship's Committee had approached Foster's to develop a small landship to cross the trenches as fighting in France reached stalemate in 1915.

Constructed in great secrecy, the machine was given the codename 'Tank' by Ernest Swinton, who had become convinced "a petrol tractor on the caterpillar principle and armoured with hardened steel plates" would be able to counteract German machine-gunners. The first prototype landship was demonstrated to Swinton and his committee on September 11, 1915, although with a top speed of 2mph over rough ground and unable to cross broad trenches, Little Willie proved disappointing. However, 141 days later, a second prototype vehicle emerged named 'Mother' - essentially an agricultural tractor with armoured body - and saw action in 1916. British Army tanks are widely held to have pushed the conflict to its rightful conclusion.

To mark the extraordinary achievements of the highly skilled workforce at Foster's, a series of plaques were made by the company and presented to both staff and suppliers. Among those in receipt was chief draughtsman William Rigby.

The vendor of the plaque, above, seen at Thos. Mawer and Son Ltd of Lincoln on June 3 recalled that 30 or 40 years ago Rigby had tried to give his notebooks and the tank plaque to the city council, but they had expressed little interest. Instead he had given them to her husband. Sadly the notebooks had been destroyed in a fire but the plaque had survived, still covered in an original factory blueprint of Mother.

Two years ago the rooms sold a similar tank plaque (although without the blueprint or provenance) to the Museum of Lincolnshire Life for around £500.

Two commission bids left on the books started the bidding for this example at £300 and two bidders in the room pushed the price upwards. It finally sold to a Lincoln man for £600.

By Roland Arkell