MacDonnell came of an old landed Clare family. Leaving Cambridge before taking his degree, he joined the army and saw service in the American war where he transferred to the volunteer regiment which Lord Rawdon raised from the Irish-Americans. At the end of the war the regiment was disbanded and MacDonnell did not return to active service until 1793. In 1794 he was appointed to raise a regiment of foot but recruiting did not proceed satisfactorily; the regiment never reached full strength and in 1798 was disbanded. In the meantime he had entered the Irish house of commons but does not appear to have taken a particularly active part. On 1 Jan. 1799, writing to Pitt with an offer to raise a regiment of fencible infantry, he claimed to be a supporter of the Irish government. The same claim had been made for him shortly before by Lord Moira, in support of his pretensions to stand at the next election for Clare, where his income was £3,000 p.a. MacDonnell voted for the Union and was promised the equivalent of £500 p.a. as his reward. His seat in the last Irish Parliament was disfranchised. In June 1801 he proceeded to Ireland with Lord Hardwicke as his aide-de-camp and military secretary and a year later obtained a commissionership of accounts, reputedly his Union reward.
MacDonnell contested Clare in the general election of 1802, temporarily resigning his place for the purpose, though he offered it for sale in a ‘peculiarly shameless’ manner. He retired after three days’ polling. He had sought government support, but the viceroy had ‘no particular wish’ in his favour and did not intervene. MacDonnell banked on defeating his cousin Sir Edward O’Brien for second place but, failing in this, accepted O’Brien’s offer to purchase him a borough seat. This ended a ‘family contest’, on which he had probably spent over £3,000.
The sequel was disclosed by the chief secretary, writing to John Sargent, 24 Dec. 1802:
Your letter of the 14th ... announcing Mr Addington’s wish that Mr Burroughs should be elected for Enniskillen reached me just in time to prevent Lord Cole from concluding his bargain with Col. MacDonnell. The day however beyond which it had been agreed that his lordship should wait no longer for Mr Addington’s answer had actually expired. Fortunately the mail of that day had not arrived. Col. MacDonnell insisted on the strict law of his case, and would have forced Lord Cole to close with him; immediately Lord Cole insistedon his equity and maintained that it was by the mail of the day and not by the day itself, that he was bound. Bloodshed and the Lord knows what was threatened—but all has terminated peacefully and well and we are very well satisfied that Mr Burroughs and not Col. MacDonnell should have attained the seat.
Wickham mss 5/5.
Soon afterwards MacDonnell made an application to Addington through Isaac Corry, who thought he deserved some attention, but did not give ‘the most favourable character of him’. An English borough seat, on Lord Holmes’s interest was found for him in February 1803—a waste of Sir Edward O’Brien’s money, as he died on 7 Sept.
