Allan, Thomas (c.1725–1798), politician and political adviser, was born in Scotland. He came to Ireland as an agent for a merchant firm trading in Pomeranian timber, and built a large fortune: first through a lottery (trading in his winning ticket brought him £9,000), and then by marriage to a Miss Greir (or Greer), daughter and heir of a successful sugar-baker, who died leaving him everything. He served in the administration (1761–3) of the earl of Halifax (qv), and was appointed taster of wines and surveyor of the outs and defects. This office had no salary, and to recover overdue fees he began legal proceedings against some Dublin merchants; in return they raised a subscription against him which was later used to establish the Royal Exchange. In 1772 the office became part of the patronage of John Beresford (qv) with a salary of £1,000 per year, and Allan received £800 compensation.
Closely connected with the Townshend family, he became a key adviser and agent of George Townshend (qv), who became viceroy in 1767. Although Allan became MP for the borough of Killybegs, Co. Donegal (1768–76), which he purchased from Lord Conyngham (qv), he was a more frequent visitor to the British parliament, especially for Irish debates. He resided chiefly in London, where he served as an unofficial liaison between the lord lieutenant and the government, acting as advocate for Townshend's policies, and preventing mischief between Dublin and London. He was also responsible for supervising visiting Irish MPs and for ensuring that they returned to Dublin for the parliamentary sessions.
He became a commissioner of the Irish customs when Townshend divided the revenue board, but became redundant when customs and excise were reunited under Lord Harcourt (qv), Townshend’s successor. His brief tenure on the customs board was competent, if unpopular, and he received an annual pension of £600 on quitting. A less active member of the government after Townshend returned to England in November 1772, he was nevertheless occasionally consulted by the new administration.
After the 1776 election he purchased a seat for Naas, Co. Kildare (1776–83), at the request of the government, but was largely absent from parliament, having negotiated a pension. He returned to an active political role in 1778 when he served as unofficial Irish adviser to Lord North, first lord of the treasury, acting as ‘unofficial undersecretary’ (HIP, iii, 82). With the collapse of North's ministry (1782), his interest in Irish affairs declined. He did not seek re-election in 1783, and withdrew from politics on the accession of William Pitt. In 1784 he was forced to retire from the English customs board (to which he had been appointed in 1776 in exchange for his Irish pension) when an eye infection worsened, and he retired to his country house at Richmond Hill, Surrey, where he died 12 June 1798. Most of his estate was inherited by his illegitimate daughter Maria Gordon (Allan).