Lethbridge was somewhat unexpectedly returned unopposed for his county on a vacancy in June 1806. Lord Glastonbury thought him ‘an improper person’ and the premier Lord Grenville was ‘rather inclined against him’, but other contenders withdrew.
The Member ‘whose name the newspapers could not learn’ and whose speech I wish they had given, was Mr Lethbridge, our Berkeley Square purchaser—who said that the landed interest were highly indebted to me for taking up their cause—so that a man buying one’s house makes him a good politician. He voted with us on Friday.
On 24 Mar. 1807 he took two weeks’ leave, but on 22 Apr. spoke in favour of the prosecution of (Sir) Christopher Hawkins.
Lethbridge survived a contest in 1807. Lord Sidmouth, who did not expect him to do so, wrote, ‘I rather wish we had assisted him though he has no claim whatever’.
On 3 Dec. 1811 Lethbridge wrote to Perceval renewing an application of two years before for a peerage for his father. He was in the government minority on McMahon’s sinecure, 24 Feb. 1812. In a further application of 9 Mar. he asked Perceval to bear in mind
the support which I have had the pride and pleasure to afford you in the country more than in Parliament, having grown out of that warm and lively admiration with which I have observed your statesmanlike and truly great qualities and attainments.
He had it in mind, if no assurances were forthcoming, to ‘withdraw from the public situation which I at present hold as well as disposing of the property which with its influence has brought so much trouble upon me’. Perceval could pledge himself to nothing.
Out of the House, Lethbridge wrote to the Speaker to congratulate him on his anti-Catholic speech, 29 May 1813: he had written for the same purpose to Sir John Nicholl on 11 Feb. When on 25 June 1815 his friend Francis Drake of Wells wrote to ask him his views on sitting in Parliament (possibly with an impending vacancy for Wells in mind) he replied, 29 June:
I have distinctly to say, that it is not only my wish to sit again in Parliament but my resolve to do so, whenever the circumstances which impelled me to retire, cease to operate. These circumstances only hold as to the county representation, and therefore I am free to sit for any other place now, which I should consider in other respects desirable.
Two great points, however are requisite, small expense in effecting the return, and a full free and unbiased choice as to my political line of conduct. The first because (unless it should be for the county another day) my anxiety to be in Parliament is not particularly great. The second, because control in politics to me would be insupportable, and is what for no consideration, I will ever submit to.
When the vacancy at Wells passed both of them by, he assured Drake, 24 July, ‘I can speak from experience, when I say, the various plagues which accompany the honour are a very serious drawback, and often induce men to regret its acceptance.
Late in 1815 Lethbridge’s father died intestate. Joseph Jekyll reported, ‘Old Sir J. L. had disinherited his son. On his death bed the son told the father he knew it. The father called for his will and tore it in pieces.’ He was now free to aspire to the county seat again. An ardent protectionist, he wrote to Lord Liverpool, 23 Dec. 1816, advocating measures to support the landed interest. At the election of 1818 he assailed the politics of both his opponents and they coalesced against him and defeated him. In the following year he was engaged in rallying anti-Catholic opinion in the county in the spring, and on 1 Nov. wrote to Lord Liverpool expressing his support of government measures against radicalism.
