Julian Rudolph Leathart was born in Lambeth, London, England on 9 July 1891. It is not know where and with whom he received his training but by the early 1920s was in practice as an architect in London. He subsequently specialised in cinema architecture By the mid-1920s he was in partnership with William Fraser Granger (1888-1969) as W F Granger & Julian Rudolph Leathart [also known as Julian Rudolph Leathart & W.F. Granger and as Granger and Leathart]. The partnership with Granger was dissolved in 1935. Leathart later formed a partnership with his son, John Anthony Leathart, and John Philip Tingay as Leathart, Son & Tingay which had offices at 49 Welbeck Street, London. This partnership was dissolved in November 1956
He died in Easthampstead, Berkshire in 1967.