Medal card : Sgt. - 25th London Regt.
Medal roll : 25th London R. Sgt., Attached Infantry Base Depot 1(a) France 21.7.17 to 8.8.17.,
                  Posted to 10th London R. 1(a) France 9.8.17 to 21.9.18.

He appears in the publication 'Soldiers Died in the Great War 1914-19' under the heading "25th (County of London) Battalion (Cyclists)" :-

Baker, Arthur Ensom, born Tottenham, resident South Tottenham, enlisted Fulham, 741785, killed in action, France & Flanders 21 Sep 1918.

In Memory of
Serjeant Arthur Ensom BAKER

741785, Army Cyclist Corps
who died age 27
on 21 September 1918
Son of Mr. G. A. J. Baker and Mrs. M. E. Baker, of "Seaward," Highcliff Drive, Leigh-on-Sea, Essex.
Remembered with honour
Honnechy British Cemetery

[Courtesy of Commonwealth War Graves Commission]
http://www.cwgc.org/search/certificate.aspx?casualty=572139
http://www.cwgc.org/search/casualty_details.aspx?casualty=572139