In the 1860s Croll described himself as a 'civil engineer' from an address at 10 Coleman Street. Perhaps this was the contracting which he did for the telegraph companies. He is said to have built the Wool Exchange in Basinghall Street but actually on the site of 10 Coleman Street. In 1873. Pevsner says that it was built by John Gordon of Glasgow of 'Aberdeen Marble. The connection with Croll - apart from the Scottish one, is not clear. In the 1870s he began to write about his experiences- beginning with a history of the Great Central Company . Journal of Gas Lighting was to review this publication as 'a romance of which Mr. Croll is the hero'.
In his later years Croll lived at Beechwood, in Reigate, with his wife, Sophia. They had no children. He died in Dunblane in 1886. It is perhaps fitting that, given his contribution to the exploitation of ammonia salts, that he died while experimenting with sulphate of ammonia.
Croll was not typical either as a gas engineer or a chemical manufacturer. Despite his pretensions - and undoubted skills - he always cut a figure of fun. He fell into vats of tar but remained totally impervious to criticism. He never seems to have been short of money despite the financial irregularities with which he was surrounded. Neither does he seem short of bright ideas. He must have been very influential in moving the chemical industry on in its relationship with the gas industry and it's by products.
There is something else which is very important. A young man was growing up in the back streets of east London while Croll was mismanaging his gas and chemical works on Bow Common. The Great Central Gas Works was at the end of his street - and it was in a Bethnal Green Gas Works that he began his career. William Perkin has been seen as the founder of the coal tar dye industry but who knows how much he learnt from his youth surrounded by the experimenters of the east end.