November 1883 to 1888, remaining as assistant for a few months after completing his apprenticeship. In the latter year he won the Soane Medallion, which together with family money enabled him to undertake extensive travels in the following two years. He set off in February 1889, his first port of call being Malta, after which he toured Italy, Sicily and France. He returned in August 1889 and it appears that he may have made an enquiry about entering the RA Schools at that time: he was certainly in contact with R. Phené Spiers, who advised him to undertake a further study tour, this time of Spain, which lasted from November of that year until June 1890. His studies in Spain were published in 1893 as the folio ‘Renaissance Architecture and Ornament in Spain’, dedicated to the Queen Regent, Dona Maria Christina. On his return from Spain he obtained a place in the office of Thomas Edward Collcutt and he passed the qualifying exam in March 1891, enabling him to be admitted ARIBA on 8 June of that year, his proposers being Collcutt, Spiers and Leiper. In that same year he commenced practice at Hastings house, 10 Norfolk Street, Strand, where he remained until his death. A second visit to Spain was made in 1893 in connection with the publication of his book. In the mid-1890s he undertook work as a prespectivist for Niven & Wigglesworth. He also formed an association with A T Bolton to submit a joint entry to the competition for Durham County Buildings.
Prentice was elected FRIBA on 3 February 1902, again with the support of Collcutt and Spiers but this time with Aston Webb as his third proposer. From 1920 until 1933 he was in partnership with William M Dean and from 1935 until 1940 with H J Scaping and Arthur Henry Wheatley.
Prentice built many Arts and Crafts houses in Gloucestershire and Worcestershire. His work was characterised by exceptional refinement. His brother Thomas was a shipowner and much of his practice consisted of steamship interiors for the Orient and the Australian and South American Lines.
Prentice died at Willow Park in his native Greenock on 23 December 1941.