The son of an actuary (Falmouth Savings Bank), auctioneer and valuer, the young artist studied first at the new Falmouth Art School, and then from 1906-8 with Stanhope FORBES. In 1909 his picture The Eve of Waterloo was accepted at the RA. 

He stayed in lodgings in Florence Place, Newlyn, with Carey MORRIS (a Welsh student from Llandeilo, Wales) who became a close family friend, especially with Tresidder's brother, Alfred. Hereward set up as a professional painter in Falmouth, painting portraits, flowers, landscapes and seascapes. After his father's death in 1914, he took over his bank position, but became a Grenadier Guard at the outbreak of the War.

Wounded at the Battle of the Somme and declared unfit for further service, he painted delicate and poignant water-colours of patients during convalescence at Torquay . He married Daisy Maud Webster in 1919; they lived in Clare Terrace, Falmouth, and had three children. He decided, due to his family responsibilities, to continue his banking work rather than try to succeed as an artist. He was one of the Forbes School of Painting's early pupils still alive to remember Forbes' 85th birthday.  Although virtually all of his work is kept within the family, in 1983 an exhibition of 66 of his paintings was held at the Falmouth Art Gallery.