Pratt remained at Dowles until 1795, when, on receiving priest's orders, he became assistant minister under
Richard Cecil, the evangelical minister of
St John's Chapel, Bedford Row. On 7 September 1797 he married and settled at 22 Doughty Street. There he received pupils, among them being
Daniel Wilson, with whom he became close friends. In 1799, at a meeting of the
Eclectic Society, which met in the vestry of St John's, he argued for a periodical publication. The first number of the
Christian Observer appeared in January 1802 under his editorship. After six weeks he resigned the editorship to
Zachary Macaulay. He set up the
Missionary Register, of which the first number appeared in January 1813. Pratt also helped to form the
British and Foreign Bible Society in 1804; he was one of the original committee, and was its first Church of England secretary, but then retired in favour of
John Owen. In 1811 he was elected a life-governor, and in 1812 he helped to frame the rules for the organisation of auxiliary and branch societies, and of bible associations. In 1804 Pratt left Cecil to become lecturer at
St Mary Woolnoth, Lombard Street, where
John Newton, another evangelical leader, whose health was failing, was rector. Next year he became Newton's regular assistant curate. In 1804 he also undertook two other lectureships, the evening lecture at
Spitalfields Church, and Lady Campden's lecture at
St Lawrence Jewry. In 1810 he was made by Hastings Wheler the incumbent of the chapel of
Sir George Wheler—the Wheler Chapel—in Spital Square, which had been shut up for some time. For 16 years he stayed there and set up the Spitalfields Benevolent Society; among his congregation were
Samuel Hoare Jr of Hampstead and
Thomas Fowell Buxton. Buxton with others left the
Society of Friends, and were baptised into the Church of England. Pratt worked to promoting the church establishment in India, encouraging
Claudius Buchanan, and urging the Church Missionary Society to give practical aid when
Thomas Fanshaw Middleton was appointed bishop of Calcutta. In 1820 Pratt corresponded with two American bishops,
Alexander Viets Griswold and
William White, and welcomed
Philander Chase,
bishop of Ohio, on his visit to England; and it was partly through his efforts that an American missionary society was established. He also supported in the mission of his brother-in-law
William Jowett to
Malta and the Levant, and founded with Buchanan the Malta mission. ==St Stephen's, Coleman Street==