the name "day's lock" comes from the day family, local catholic yeomen since the 17th century. during the 16th century, there was a flash lock here. the pound lock was staked out in august 1788. it was judged best to build it on the oxfordshire bank provided the existing weir owner would "remove his bucks"(eel traps). in 1865 it was reported to be in utter ruin and dangerous, but reconstruction did not take place until 1871. in 1882 a bell push to summon the keeper was installed, there being no lock keeper's house at that time. the lock house was not built until 1928 when it was erected on lock house island next to little wittenham bridge.