In what's becoming the grand tradition of 'Comic Firsts', the strip below isn't the first strip drawn by Eric Bradbury by a long shot -- but it is, I believe, his first adventure strip. Lucky Logan, the happy-go-lucky cowboy, first appeared in Knockout no. 756 (August 22, 1953).
At 4 pages a week, Lucky Logan was twice the length of most adventure strips in Knockout and a second artist came in a couple of issues later to alternate with Bradbury. Mike Western was already a friend of Bradbury's, the two having worked together at G.B. Animation; when the latter closed down, Mike went off to join Halas & Batchelor to work on Animal Farm whilst Bradbury went to the Amalgamated Press, working with Ron Clark on humour strips. His first job was a filler called Blossom and here, as a bonus, is the very first Blossom strip, published in Knockout no. 612, undated but printed in August 1950.
(* Lucky Logan and Blossom are © IPC Media)