Calvert was heir to the Hertfordshire, Essex and Cambridgeshire estates of his father, the ‘eminent brewer’. Hunsdon, settled on him at his marriage, became his residence in 1801 and he proceeded to rebuild it. His wife, an Irish beauty, became one of the hostesses of the day and the personable couple were members of the Prince of Wales’s set. In 1802 Calvert succeeded his kinsman John Calvert of Albury to a seat in Parliament for Hertford. His father was a Whig, interested in finding a seat in 1790, and Calvert was described in his obituary as having ‘from the commencement of his parliamentary career supported Whig principles and parliamentary reform’.
In fact he appeared in the minority during Addington’s administration only on the question of the Prince of Wales’s finances, 4 Mar. 1803, and in May and September 1804 was listed Addingtonian. He had called for the parties guilty of bribery in the Ilchester election to be brought to justice, 22 Apr. 1803, objected to taxation of farm horses, 15 July, and called Aylesbury ‘one of those jobbing boroughs, all of which he should be happy to see thrown open’, 23 Mar. 1804, though he opposed the prosecution of Robert Bent for bribery, 9 May. He voted against Pitt’s additional force bill in June 1804. According to his wife, he offended the Prince of Wales by voting with ministers early in February 1805, but resumed voting with opposition on defence, 21 Feb. It was he and not John Calvert II who voted for Sheridan’s motion to repeal the Additional Force Act, 6 Mar. On 1 Mar. he had voted for his neighbour Daniel Giles’s motion to continue the naval commission of inquiry. He went on to vote in censure of Melville, 8 Apr., his wife reporting the Prince as saying that Calvert, rather than Whitbread, should have moved it, ‘as coming from an independent man it would have had still more effect’; was proposed by Whitbread for a select committee on the subject, 25 Apr., and voted for the criminal prosecution on 12 June. He was accordingly listed ‘Opposition’. His only known speech that session was for further exemption for charities from the property duties bill, 5 Apr. On 15 Jan. 1806 his wife reported that the opposition had requested Calvert to second their amendment to the address, but ‘were he inclined to do so, he would have no time to prepare a speech’.
Calvert was well disposed to the Grenville ministry. He voted for the repeal of the Additional Force Act, 30 Apr. 1806. He defended the training bill, 26 June, though he doubted if it would be effective without provision for Sunday training. On 6 June he was a spokesman for the brewers against taxation. He welcomed the finance committee, 10 Feb. 1807, as an instrument for regulating sinecures and pensions and was appointed to it, but doubted if its modus operandi would achieve the object, 11 Feb. He befriended Whitbread’s Poor Laws bill, 19 Feb. 1807, but opposed the freehold estates bill, 11 Mar. He complained, moreover, that the landed interest were treated by government as ‘sheep to be sheared’, 18 Mar., and acted as opposition teller that day. On 9 Apr. he returned from leave of absence to vote for Brand’s motion against the Portland ministry, taking fresh leave on 15 Apr.
Calvert was, at first, ‘even violent’ in opposition after the election of 1807, as his votes on 26 June and 6 July confirmed. It was on 23 July that he joined Brooks’s Club, sponsored by Lord Howick. He would not act with opposition on the Copenhagen expedition in 1808, but he voted with the minorities against the new military plan, 14 Mar., against the Scottish legal pensions, 4 May, and favourably to the Irish Catholics’ cause, 29 Apr., 5 and 11 May.
Calvert was not present at the Whig pre-sessional meeting in January 1810, but he voted steadily against ministers on the Scheldt question and against the committal of Burdett to the 5 Apr., though he opposed the release of Gale Jones, 16 Apr. He voted for parliamentary reform on his friend Brand’s motion, 21 May, and for supervision of the droits of Admiralty, 30 May. On the King’s illness he voted with ministers for the adjournment, 29 Nov. 1810, but with opposition on the Regency bill, 1 Jan., and, after a Whig circular to attend, on 21 Jan. 1811. The Prince’s assumption of the Regency seems to have qualified his attitude. On 4 Feb. 1812 he was swayed by the Irish secretary into voting against Morpeth’s Irish motion.
Calvert headed the poll and was the only well received candidate at Hertford in 1812.
