Manning’s father, of a St. Kitts planter family, settled in London in the 1760s as a West India merchant. He himself was a partner in the family business successively with his father, his brother-in-law Benjamin Vaughan and subsequently with Anderdon and Bosanquet. Through his mother, he inherited two parts of an estate on the Danish island of Santa Cruz and purchased the third. On coming into his inheritance, he became a director of the Bank of England and in 1793 a commissioner of Exchequer bills. He was brother-in-law (through his first marriage) of Robert Smith and moved in Pitt’s circle, being also friendly with Bishop Tomline and with Wilberforce.
Manning was described in 1806 as ‘a man of most conciliating manners with a good head and a good heart. In politics he is decidedly in favour of government’.
Manning next became involved in the West India merchants’ lobby for a new wet docks at Wapping to remedy the deficiency of the port of London. On 3 Feb. 1796 he submitted their petition and plan to the House. Against opposition from the corporation of London, he secured a select committee and a bill, 18 Feb. On 16 Mar. he secured Pitt’s goodwill for its second reading, the City having failed to provide a better plan, but gave it up that session, renewing the project on 30 Nov. 1796. The bill was again opposed, 9 Dec. 1796, 15 Feb. 1797, despite alterations to meet its critics. In June 1799 Manning was forced to swallow the London port improvement bill which situated new docks at the Isle of Dogs, though he made a token opposition to one clause, on which he twice divided the House. He secured government assurance that the West India merchants might subsequently pursue their own plan and on 21 Feb. 1800 introduced a new bill for wet docks at Wapping. Government helped him to thwart a City petition for counsel to renew their case against it, 10 Mar. He pointed out that the dock company’s outlay of over £700,000 was for the general benefit, not merely for the West India merchants. This time he succeeded and between 1803 and 1806 secured further legislation to expand the docks.
On 22 and 27 Mar. 1797, Manning first spoke as a Bank director, vindicating the Bank’s conduct in the stoppage of cash payments and emphasizing its independence of, and services to, the government. On 30 May he held out hopes of a speedy resumption of payment in specie. He had subscribed £10,000 to the loyalty loan for 1797 like other directors and on 1 June asked the Speaker whether his interest disqualified him from voting for the subscribers’ bonus. The Speaker’s reply decided him not to vote. He joined the London merchants’ censure of the naval mutiny.
Manning would not hear of allegations that the Bank profited at the expense of the public: ‘the man who looked to profit, was unfit to be a director’ (21 Mar. 1800). On 23 Apr. 1800 Pitt secured his endorsement for a parliamentary authorization to export bullion to the allies. He also supported Pitt’s income tax against Tierney, 5 June. In the sessions of 1801 and 1802 he resisted the attacks on the Bank of the ‘three Horatii’, Richard Bateman Robson, John Nicholls and Thomas Jones, and on 9 Apr. 1802 justified the continuation of the stoppage of cash payments for the time being. He opposed the opening of malt distilleries, on behalf of the West India sugar planters, 14 Dec. 1801. He had opposed relief for the West India merchants of London, 2 Oct. 1799, but approved the loan to the Grenada planters, 30 Mar. 1803. On 31 Mar. 1802 he was in the minority for inquiry into the Prince of Wales’s finances. He was appointed to the civil list committee on 2 Feb. 1804.
Manning said little in the House during Addington’s ministry, but it is clear that his attachment was still primarily to Pitt, for he was in the latter’s minority of 3 June 1803 and again on 25 Apr. 1804. He was listed a supporter of Pitt’s second ministry, but inactive except on the slave trade question. In a previous isolated speech of 11 Apr. 1796 he had opposed a bill to improve the slaves’ lot on the grounds that it might be left to the colonial assemblies. On 30 May 1804 he disclaimed opposition to abolition, but called for a guarantee of compensation to the slave owners, rejected by 124 votes to 49. On 12 and 13 June he again failed in a bid to obtain a committee on compensation to accompany the bill. On 2 May 1806 he pointed out that the Spanish colonial coastguards winked at British imports on vessels carrying slaves. He renewed pressure for compensation, 10 June 1806, and was listed ‘adverse’ to abolition, but explained, 23 Feb. 1807, that he did not think it harmful. He had no plantation in the British colonies, only on Santa Cruz, where there had been no slaves imported since 1793. On 17 Mar. 1807 the House was counted out when he attempted to relate his own experience in the colonies.
Manning favoured the public payment of Pitt’s debts, 3 Feb. 1806, though he was sure they could have been met by private subscription. He disliked squandering public money and recalled his voluntary contribution to the war effort. George Rose, however, reported that at the meeting of Pitt’s friends the week before, he offered just £100 for the purpose.
Manning was as prepared to support the Portland ministry as its predecessor. On 10 Feb. 1808 he was a spokesman for the Bank against critics of its charges for managing the public debt, which, he pointed out, occupied half of its 800 clerks. He was, without soliciting it, a member of the select committee on distillation that session (having taken the chair in a previous one early in 1807) and, denying any bias, favoured distillation from sugar to save the West Indian colonies from ruin, 13 Apr., 3 June. He acquitted the Duke of York of corruption, but voted that he had been guilty of allowing an improper influence (that of his mistress) in army patronage, 20 Mar. 1809. He was in the majority for the address when Perceval’s ministry met Parliament, 23 Jan. 1810, but for the inquiry into the Scheldt expedition on 26 Jan. and complained on 29 Jan. of the tendentious way in which the Morning Chronicle had published the division lists of the 23rd, as if those who voted for the address were opposed to the inquiry. But he rallied to ministers on it, 23 Feb., 30 Mar., being listed ‘Government’ by the Whigs.
Next in line for the chair of the Bank, he applied to be on the bullion committee of February 1810
Manning was spokesman for the Bank in the House only once (8 Dec. 1812) for the remainder of his term as governor. The father of Cardinal Manning, he opposed Catholic relief on 2 Mar. and 11 May 1813, but was neutral on 24 May. It was a subject on which he subsequently wavered, voting for in 1815, against in 1816 and for in 1817. In 1813 he spent over £40,000 on the purchase of Coombe Bank from Lord Frederick Campbell.
In the session of 1817, Manning was in the government majorities of 7 and 17 Feb., opposed inquiry into Bank affairs, 19 Feb. and reproached Burdett for bringing in masses of reform petitions with no knowledge of their contents, 3 Mar. He refused to countenance any measures against alien investors in Bank stock, 7 May. He voted with ministers on the operation of the suspension of habeas corpus, 10 Feb., 5 Mar. 1818, but against them on the ducal marriage grant, 15 Apr. That session his speeches were confined to Bank affairs, opposing resumption, but not an inquiry into it (4 Mar.) and justifying its procedure in cases of forgery. He was appointed to the secret committee on the Bank in 1819, but not, he insisted, in an official capacity. The Bank did not take sides on the question of resumption, but had been acting on the assumption that it was imminent (2 Feb.). He concurred in the cash payments bill, 5 Apr., but on 24 May objected to the schedule for resumption and on 14 June pressed for the speedy repayment by government of half its £10 million debt to the Bank. This motion was defeated by 166 votes to 21. He persisted in the view that the Bank should have the right to decide the timetable for resuming cash payments, 25 June.
Manning, who subsequently developed Australian interests, called for a fair hearing for Governor Macquarie in debate, 23 Mar. 1819. On 8 Apr., bringing up the report of the Camelford election committee, he declared that evidence of bribery was not proven and moved for a new writ. It was carried by 103 votes to 15. He opposed the Penryn bribery bill, 12 May, and voted against the extension of the franchise there, 22 June: but his partner’s son, John Lavicount Anderdon had been a candidate there in 1818. He voted against public lotteries, 4 May. He supported ministers against Tierney’s censure motion, 18 May. His only known gesture during the next session was to vote against the seizure of arms bill, 14 Dec. 1819.
Manning had resumed his seat for Lymington on the same interest in 1818, but intended to retire in 1820. At some stage he had refused a baronetcy. A year later he resumed his seat. He later suffered from the depression in West Indian trade and went bankrupt in 1831.