How long did it take William the conquer to build his castle?

Answer 1

Your question implies that king William I only built one castle ("his castle"), which is a false assumption.

In fact his army brought pre-fabricated wooden sections for castles with them when they invaded, to fortify his landing site and its vicinity - the initial Norman earthwork castle at Pevensey (inside the Roman fort there) was built in just a few days, followed by the motte-and-bailey at Hastings using the pre-fabricated wooden sections.

Very soon after the invasion the Normans erected a string of Castles at Dover, Canterbury and Rochester (all motte-and-bailey types) to protect their line of communications with the coast, followed by castles in London and elsewhere in the south of England.

A huge number of motte and bailey castles were then constructed around the country under William's rule, most of which were later rebuilt in stone under Henry I.

All motte-and-bailey castles were erected very quickly, using local Saxon labour and the simplest of tools: spades, mattocks and baskets to move soil and clay.

William's stone royal palace in the south-east corner of London was begun around 1077, but it was not completed until around 1100 (after William's death). It is known today as the Tower of London.