sentences:  It is believed to have been constructed as early as 1643, to fortify the crossing point of the River Great Ouse.Many fenland inhabitants resented the Royalists because they believed that the King's drainage projects undertaken by Dutch engineer Cornelius Vermuyden, had damaged their livelihoods (his Forty Foot Drain had been completed in 1637).Today, the fort is visible as a series of earthworks only, showing a bastion fort design with ditches and corner bastions.