The practice was established in 1873 by Samuel Reuben Ginn, the son of a St Ives’ solicitor, at his offices in Alexandra Street, Petty Cury.

Matthew had attended St John's College, Cambridge and served as President of the Cambridgeshire Law Society.

During the First World War, Captain Dennis Barton Ginn saw service in Dardanelles at the Gallipoli Campaign and in Egypt, Palestine and France.

He went on to become Major "Skelly" Ginn who used his electrical engineering skills to help to mastermind some of the most daring escape attempts from Oflag VI-B, Colditz and other German PoW camps during the Second World War.

In 1934 Samuel Reuben Ginn died aged 82 and left an estate valued at some £5.5 million today with 150 acres of land in Huntingdonshire.

In the same year his eldest son, Samuel Marsland Ginn, was admitted as a partner after reading law at Trinity Hall, but shortly afterwards saw service in the Second World War.

In 1939 he became a partner and together with Geoffrey Garland Goodman oversaw the expansion of the firm after the War and its relocation to the newly built neo-Georgian, Sidney House on Sussex Street.

In 1971 Ginn & Co instructed Donald Keating QC in the Mitchell v East Anglia Regional Health Board Administration case.