[1] Sir Guildford's great niece was Margaret Patricia Molesworth (1904–1985), the grandmother of Sophie, Duchess of Edinburgh.

[2][3] Molesworth and his four brothers - William, solicitor John "the calculator", George and Rennell - were educated at the King's School, Canterbury where he found football "a great attraction".

He then attended the College for Civil Engineers at Putney, apprenticed under Mr Dockray in the London and North Western Railway, and under Sir William Fairbairn at Manchester.

[4] He became a chief assistant engineer of the London, Brighton and South Coast Railway, but soon resigned to conduct the constructions at the Royal Arsenal, Woolwich, during the Crimean War.

He received the Watt Medal and the Manby premium in 1858 from the Institution of Civil Engineers for his paper on Conversion of Wood by Machinery.