Holgate Windmill.

We've left Bridlington and are now visiting friends in York who took us on a whirlwind tour of the city during this afternoon.
The highlight was seeing Holgate Windmill, restored last year to full working order complete with a back-up electrical motor and now one of only two working mills in East Yorkshire. There is a history of using alternative power in mills, this one had a steam engine added in 1859 which was replaced by the electric machine in 1930.
Originally built in 1770, it was operated by the family of the original owner for ninety years
It is fitted with five double shuttered sails making it the only one like it in Britain.
A round-a-bout and housing estate now surround the mill which is built to the "Lincolnshire pattern," a concept designed by John Smeaton who achieved fame was as the designer and builder of the Eddystone Lighthouse.
The blip is of a detail of the mechanism for adjusting the sail shutters (the shutters operate in a similar fashion to Venetian blinds).
The one question that bothers me is, "Why five sails?" This makes the design and construction difficult with normal hand tools due to the odd angles involved while an even number of sails would mean that if one sail was damaged the mill could still function if the opposite sail is adjusted to balance the system.
There is plenty of good information and on Wikipedia if you wish to follow up more technical stuff.