BRENT RESERVOIR.

https://en.wikipedia.org/

Yet another london lifer today with SPOTTED SANDPIPER putting me on (278).

Brent Res.

Trust me the bird is on the right standing on a tern raft. Spotted Sandpiper
Spotted sandpiper London records: 

• pre-1852: Brent Reservoir (Middx), one shot on an unknown date (Harting, 1866)
• 1956: Hilfield Park Reservoir (Herts), one on September 2nd (LBR 56, Hardwick & Self)
• 1988: Barn Elms Reservoir (Surrey), a summer plumaged bird on May 16th (LBR 56, Hardwick & Self)
• 1989: King George V Reservoir (Essex), one from September 25th to October 6th (LBR 56, Hardwick & Self)

The specimen of the first record was among a collection sold in April 1852 and purchased by Frederick Bond "who traced it to the person who had received it in the flesh and stuffed it and fully satisfied himself of the truth of the statement" (Harting, 1866). The specimen is now in the British Museum.