Cookham Lock is a lock with weirs situated on the River Thames near Cookham, Berkshire. The lock is set in a lock cut which is one of four streams here and it is surrounded by woods. On one side is Sashes Island and on the other is Mill Island connected to Formosa Island, the largest on the non-tidal Thames.There are several weirs here. Hedsor weir was placed across the old navigation channel in 1837, seven years after the lock was opened. There is a lower weir, and Odney weir is on the channel next to Formosa Island.A short distance away from the lock is Odney, with the Odney Club situated on an ait. Navigation to the Odney Club by boat is possible, but is extremely difficult due to the shallow waters. It is thought that this is deliberate - to disallow non-members from entering the club site without paying the entrance fees.HistoryThe navigation route was formerly down Hedsor Water and the only weir was associated with the mill. After the building of Marlow Lock in 1773 there were problems with shallow water upstream, and the earliest suggestions were for a stop at Cookham to hold the water back. In 1794 it was considered one of the most dangerous parts on the river, mainly on account of chalk boulders falling into the Thames. Plans for a lock and cut were formulated in 1807, but seven years later, the City of London were complaining that no action had been taken. In 1826, a barge carrying stone for Westminster ran aground, swung across the channel, and broke in two, resulting in the loss of the cargo, valued at 40 pounds. Finally, a cut and lock were agreed upon in 1829, the cut going through the northernmost island called The Sashes. Part of the cut was formed from an existing Sashes Stream, and an Ait was removed at the lower end of the cut. The lock opened on 1 November 1830, but no weir was built at this time. The lock and cut cost £8,400 to construct, and the fall on the lock was about 2ft.