The Institution of Mechanical Engineers (IMechE), of which Gresley was President in 1936, has produced two interesting pieces of content on Sir Nigel Gresley.

This YouTube video examines class A4 No. 4498 Mallard’s record run on 3 July 1938 in detail:

Did Mallard Really Hit 126 mph? Engineer Investigates

The IMechE has also published an article detailing his membership of the Institution:

From The Archives: Sir Herbert Nigel Gresley