Thomas Ashby was born in Staines in 1874, only child of Thomas Ashby Sr. (1851–1906) and his wife, Rose Emma, both Quakers. The family business, the Staines Brewery, was converted to a private company in 1886 and in 1890 Thomas Ashby Sr. left the company and settled in Rome for health reasons. Ashby was educated at Winchester College, subsequently winning a scholarship to Christ Church, Oxford where he obtained a First in Greats in 1897. He divided his time between England and Italy until he graduated and was awarded a Craven Travelling Fellowship; from then on, Rome became his home. He became the first scholar of the newly founded British School at Rome in 1902 and subsequently Director from 1906-25. He tragically died in 1931, at the age of 56, falling from a train at Raynes Park, on his way to Oxford to begin a Senior Research Studentship awarded by his old college, Christ Church.

Thomas Ashby was Director of the BSR for 19 years and his achievements were remarkable. Topographer, archaeologist, art historian, bibliophile and photographer, he also oversaw the move of the BSR from its original home in an apartment in the Palazzo Odescalchi in the centre of Rome, to its new building in the Valle Giulia, near the Borghese Gardens, designed by Edwin Lutyens. During World War I Ashby was driving ambulances for the British Red Cross on the Italian-Austrian front. In 1921 he married Caroline May Price-Williams. His many publications include The Roman Campagna in Classical Times (1927), the culmination of his life’s work studying the topography and archaeology of the Roman countryside; The Aqueducts of Ancient Rome (1935), published posthumously and edited by I.A. Richmond; the completion of the late S.B. Platner’s publication The Topographical Dictionary of Rome (1929); Some Italian Scenes and Festivals (1929). Illustrating his wide-ranging interests, his many projects included excavating in Wales at Caerwent and in Malta, a study of the archaeology and anthropology of Sardinia, as well as research on the Cassiano Dal Pozzo collection at Windsor.