The name sounds no weirder than some of the foreign places with which English towns are twinned. But motorists will search atlases in vain this weekend when they see signs on the borders of Wincanton announcing that it is "twinned with Ankh-Morpork".

For the Somerset market town links itself tomorrow with the lawless metropolis of Terry Pratchett's award-winning Discworld fantasy stories.

Discworld has brutish soldiers, vampires, talking mice, dwarves who turn base metals into gold, and a "cold, cunning" ruler called the Patrician. Wincanton has only its peaceable, self-effacing mayor, Frank Foster. But Mr Foster will sign the illuminated twinning certificate with the Patrician (represented by an actor), who has temporarily waived his rule that all Ankh-Morpork documents must be written in blood. Then everyone will adjourn to play Discworld's favourite board game Thud!

More than 1,000 fans from as far away as Australia are expected to attend the twinning ceremony. Wincanton hopes to boost tourism by making the link with Britain's second highest-selling author after JK Rowling.

The idea came from Bernard Pearson, a potter whose local shop, The Cunning Artificer, already has a lucrative line in Pratchett memorabilia. As for the road signs, a spokesman for South Somerset district council said yesterday: "They will certainly get people talking".