The building was a memorial to the alumni of the school who had perished in the First World War, and he donated his services free of charge. He had begun the work on the last part of County Hall in 1928 but it remained uncompleted at his death.

In 1919 Knott married Ada (née Brown), widow of Sidney James Longden. They had no children. He died suddenly at his Mortlake home in January 1929, aged 50. A bronze plaque to his memory at County Hall was unveiled by the