Harold James Druett:

The cap badge and shoulder titles are for the Queen Mary's Own 18th Hussars, a cavalry regiment with a long history dating back to 1759.

The 18th Hussars were part of the 1st Cavalry Division, 2nd Cavalry Brigade and saw service in France from 1914 (as part of the British Expeditionary Force).

Where and importantly when this photograph was taken is not known.