This postcard portrait, unfortunately with no photographer's details, has a rudimentary "aeroplane in the clouds" board cut-out backdrop, in which a young man in flat cap poses, complete with cigarette dangling from the corner of his mouth. His "rabbit in the headlights" expression doesn't give him a very comfortable look. The design is an interesting variation on the older and far more common rowboat prop used by seaside photographers since the 1880s. The clothes which the young man is wearing, combined with the apparent early design of "flying machine," suggest to me a date of between 1905 and 1910.
The divided back of the design on the reverse only tells us that it was after about 1902, when British postcards first appeared with divided backs. The text, "This space, as well as the back, may now be used for communication, but for inland only," suggests a date of between 1902 and 1906, after one could send side-by-side message and address cards to other countries. [Source: Family Photographs 1860-1945, by Robert Pols, publ. 2002 by the Public Record Office, ISBN 1-903365-20-1] It measures 88 x 138 mm, which approximates to the "standard size" of post cards (89 x 140 mm) introduced in November 1899.