A bit of detective work, and I THINK that this man was not born MARSHALL - but that is how he married, served and died. He is filed as MARSHALL in the WW1 Service Records (WO 363):

Ernest Wilton Blake MARSHALL joined the Rifle Brigade on 9 September 1914. He served as Regt No. 2936 and was killed in 1915.
He declared his age as 29y 15d, born Shanklin, Isle of Wight.

However ... Ernest Wilton BLAKE was born Q4 1885 Marylebone - no mmn, so I assume his mother was BLAKE (and unmarried).
He declared siblings all of whom are registered Isle of Wight to a MARSHALL-BLAKE marriage, so I assume he was raised with his step-father's surname.
He married Violet ARNOLD in Hackney in 1915. (She re-married a KITTERIDGE in 1917).
No Children.
Parents: William J & Eliza.
Brother: William George (Q1 1892) known as George
Sisters: Louie Marguerite (Q2 1890) & Ethel Marian (Q1 1894) known as Louie & Marian

Anc****y, MAR, pages 12371-12400