On the death of his wife, he went as assistant to Samuel Reynolds, a surgeon at Stoke Newington, whose sister he married, and with whom he entered into a partnership which lasted fourteen years.
He entered enthusiastically into the tractarian movement from its commencement, doing all in his power as a layman to forward it; he became friends with most of the leaders, especially Edward Bouverie Pusey, and his whole life and means were spent in promoting the interests of this section of the Church of England.
He parcelled out the parish of St Matthias, Stoke Newington, and was the chief agent in the building of its church, completed in 1853 to the designs of William Butterfield.
Brett thought that the Dissenting chapels such as Newington Green Unitarian Church were attracting worshippers in part because the Anglican pews were full.
He did other practical good work in founding the Guild of St Luke, which consists of a band of medical men who co-operate with the clergy.