Michael was the youngest child of Richard Horatio Edgar Wallace [1875-1932] the writer, and his first wife, Ivy Maud Caldecott. He had a brother and a sister and a half-sister, the writer Penelope Wallace. His parents were divorced in 1918. His mother died in October 1926.

In November 1929, he returned to England from the United States on the Berengaria, travelling First Class with his stepmother, and his siblings. They gave their address as Portland Place.

He was educated at Oundle and Matriculated in 1935. He was up at Christ Church for only two years.

In March-April and June-July, 1934. Esmond and Giles Romilly published the first two of the four issues published, of “The Anti-fascist Public School Magazine”. It, proudly, declared itself to be banned in Cheltenham, Uppingham, Wellington etc (Wellington being the editors' own school). It was distributed by the Parton Bookshop.

There were substantial editorials by the two editors, who were nephews of Winston Churchill. In addition, Esmond Romilly contributed “The Case Against Fascism” and “Gangsters or Patriots? - How Britain Built Her Empire.” Giles Romilly contributed “Morning Glory (Sex in Public Schools).”

Gavin Ewart (also at Wellington) contributed two short poems to the first issue and a double-page poem to the second. Other contributions included ''Blackshirts' Lament'', ''In Defence of Fascism'' by Michael Wallace, Leader of Oundle School Fascist Youth Group and ''Side-light on the Blackshirts''.

In October 1938, he arrived in England describing himself as a student who had last lived in France and giving his address as E1 Albany, London.

He joined the Queen’s Own Royal West Kent Regiment and he was killed on 15 May 1944.

“The London Irish were scheduled to attack on the afternoon of 15 May in parallel with the Lancashire Fusiliers of the 11th Brigade to their right. But just before the scheduled time of the attack, a barrage of shells fell on the battalion’s headquarters, killing London Irish commander Ion Goff and the commanding officer of the supporting tank unit. Other officers were killed and wounded. Major John Coldwell-Horsfall, who had been appointed second in command of the London Irish in March, took over leadership of the battalion. The attack was delayed until 7.30pm.

It had been another bitter day for the 8th Army. Many young men had died. They included Michael Blair Wallace, son of the English writer Edgar Wallace who was then aged 28 and a lieutenant in the 1st Battalion of the Queen’s Own Royal West Kent Regiment. It had been in action as part of the 4th Division since 12 May on the right of where the London Irish were waiting for the order to advance that evening.”

He is buried in the Cassino War Cemetery Plot XII. K. 4.

His obituary in The Times stated that he “was the husband of Betty, the youngest son of the late Edgar Wallace and brother of Pat, Bryan and Penelope”. 

Probate was granted to his wife, Elizabeth Katherine of Surrey Lodge, Claygate, Surrey. He left £3259-18s.