Lowndes’s family was of long standing in Buckinghamshire, which his grandfather had represented from 1741 to 1774. Thomas James Selby of Whaddon, a former sheriff of the county, who died in 1772, left directions in his will that, in default of rightful heirs, the estate should go to Lowndes’s father, on condition that he assumed the name of Selby. After litigation, his claim was recognized in 1783. On succeeding to the Whaddon estate in 1813 Lowndes himself took the additional name of Selby, ‘out of respect for the memory’ of his father’s benefactor.
Lowndes was returned unopposed for Buckinghamshire on an independent platform at a by-election in January 1810 following the lapse of the Portland interest, and retained the seat until his retirement at the dissolution of 1820. He voted with government on the address, 23 Jan., but against them on the motion for the production of Lord Chatham’s narrative concerning the Scheldt expedition, 23 Feb. 1810. The Whigs accordingly classed him as ‘doubtful’ in mid March, but he voted with them on Porchester’s resolutions condemning the Scheldt expedition, 30 Mar. 1810, and, according to Canning, would have voted with him had he decided to oppose government on the resolution approving the retention of Walcheren.
The Liverpool government numbered him among their supporters after the 1812 election and on 30 Sept. 1813 Thomas Le Mesurier, informing Lord Sidmouth of a mild complaint by Lowndes of ‘something like inattention’ to his claims to constituency patronage, described him as ‘a firm friend of government’.
