The earliest reference to a
flash lock is in the late 16th century, although a mill is known to have existed here in the 14th century. The flash lock was located in what is now the main weir, with a winch to haul barges through on the west bank near the tip of Boulter's Island. In 1746 it was written that there was no (extant) lock further downstream on the Thames. The Thames and Isis Navigation Act 1771 (
11 Geo. 3. c. 45) obtained on 29 April 1771 did not allow the Thames Navigation Commission to build locks below
Maidenhead Bridge, so the lock built here in 1772 was the furthest downstream of the eight first built by the commission. The lock was timber-sided, and the work was overseen by Joseph Nickalls, who had designed a scheme of improvements to the river from Abingdon to Richmond, in preparation for obtaining the
act of parliament. Originally the lock was on the
Taplow side, close to Taplow Mill. It was referred to as Boltus lock or Bolters lock. A "bolter" was a
miller and referred to the mill of Taplow. In 1773 a resident landowner complained of trespass in his woods by barge crews who "very much misbehaved themselves by their indecent conversation and horrid oaths and imprecations." Its prototype lock-keeper's house was built here in 1774. By 1780 the lock was reported as being in as bad a state as Marlow, and in 1795 Phillips
Inland Navigation complained of the deep hole and subsequent shoals caused by the force of water. In 1825 the City of London Corporation complained regarding condition and recommended it be rebuilt on the Berkshire side of the river. This involved excavating a lock cut. For drainage during construction, a
waterwheel was placed in the weir, which was used to operate pumps. The contract to dig was given to George Gynell, at a cost of £1,630. A separate contract for the masonry and millwright's work was given to Clarke and Moss, while carpentry and general labouring was done by men employed directly by the commission. Stone was obtained from
Headington Quarry near
Oxford. Because of the distance from the fall below to the lock, a separate steam engine was used in operation post-building to pump out (lower) the lock chamber. The project was managed by George Treacher, with work beginning in December 1827 and finishing in April 1829. The total cost of the work was £11,800 When completed, the lock's volume – length with a fall of plus depth of over the sills—was the largest of a pound lock with masonry walls on English river navigations. In recognition of his work, Treacher was awarded £100 by the Commission in June 1829. The new lock was known as Ray Mill pound after Ray Mill Island next to it. The lock cut created
Boulter's Island. This part of the river became popular for boating parties in the late 19th century and early 20th century, as portrayed in a painting by
Edward John Gregory. The lock was a popular place to visit on the Sunday after
Royal Ascot when the wealthy and famous passed through the lock, some on their way to
Cliveden. In 1899 an iron railing was placed round the lock to keep spectators at bay. In 1909 the
Thames Conservancy purchased Ray Mill Island to provide for expansion of the lock, and it was rebuilt in 1912. Congestion at the lock was a serious problem before
World War I, and a novel solution was employed to reduce it. A moving ramp, consisting of wooden slats with chocks to prevent rowing boats from rolling over, was constructed to bypass the lock. The ramp was similar to an
escalator, and small boats simply rowed towards it, and were carried up to the higher level while the occupants remained seated in their boat. The boat lift opened in 1909, and was powered by an electric motor. The date of its demise is uncertain, but its location on Ray Mill island can still be visited. The
salmon ladder opened at Boulters Weir on 19 May 2000 by the
Duke of Wellington was the last of a series built on the Thames. The last salmon caught at the weir was landed on 5 August 1993. It is to this day the largest salmon in recorded history caught on the non-tidal River Thames and weighed 14lb's, measuring 97 cm's in length. ==Access==