Answer - the Saltaire Dining Hall

This is the answer to yesterday's puzzle....the door seals up a tunnel, which - when Salts Mill was thriving - led from the Mill, under Victoria Road and into the Saltaire Dining Hall, shown here.

Titus Salt was a caring employer, but also a wise businessman, realising that his workers would be more productive if they were well-fed. The Works Dining Room provided subsidised meals at a set price - a bowl of porridge and milk was 1d (one old penny), a helping of meat and potato pie was 2d, and a cup of tea was 1d. The Hall seated between 700 and 800 people. It cost £3600 to build and was paid for by a levy on Saltaire tenants. Completed in 1854, it is one of the oldest buildings in the village, after the Mill itself. It meant that workers who had to travel into Saltaire (before the housing was built) could get a decent meal every day.

I don't know whether they grew their own veg and potatoes for the Dining Hall, but it is possible. The driveway at the side leads to some allotment gardens. The building is now part of Shipley College.