Thomas Myddleton Shallcross was born in Huyton, Lancashire, England in 1862. He was active as and architect in Liverpool in the early years of the twentieth century and was for a period in partnership with Sidney Pelham Morter (1869-1933), William Glen Dobie (1866-1957) as Shallcross Morter & Dobie. In 1909 they entered a competition to design new County Hall Offices and Committee Rooms, etc. in Reading, Berkshire. Their designs are illustrated in British Competitions in Architecture vol. 3, no. 29, March 1910 (pp. 152-154). The practice had an office at The Temple, 24, Dale Street, Liverpool.
Shallcross exhibited at the Royal Academy in London in 1904-05. A grand piano designed by him and made by Broadwood & Sons is illustrated in 'The Studio' November 1901 (p.135).
His address was given as 6 Dale Street, Liverpool in 1905. He died in Liverpool, Lancashire on 7 March 1919