At an ordination service for a missionary, to which both had been invited, Spurgeon noted how extraordinarily different they were: he found Brock's delivery to be "massive, ornate, rich in words, too ponderous for our tongue, and in terms which would have suited none but himself", but, he generously added "it was ’homely, hearty, intense, overwhelming; it did our soul good".

He became, to use his own words, "churchless, wifeless, homeless" in one week, and adapted to retirement from Bloomsbury Chapel by renting rooms in Hampstead (close to where his eldest son lived) for the summers, whilst, during winters, he "hibernated" as he called it, on the south coast, at St. Leonards, where the air was fresher and the climate milder.

Brock was, therefore, opposed to warfare at the time of the Crimean War and Siege of Lucknow but nevertheless wrote a well-researched biography of the life of General Sir Henry Havelock, who was a fellow baptist.

However, he was widely criticised by those who would not buy his book, including friends in the Baptist ministry and Peace Society, for attempting the portrayal of a Christian who was also a soldier in complex contemporary political and military events.

At an early stage in this work, he appears as a delegate in the painting of the world's first international Anti-slavery Convention in 1840, which hangs in the National Portrait Gallery in London.