This is HMS Obdurate. To show their appreciation for the boys at Vanbrugh Castle who supplied the trebles in the choir at the Royal Naval College, the college arranged a day's outing each year. This was the only reward the boys received for their efforts and the trip was usually to a naval destination.
In later years VCS choir boys were given pocket money for their services, but did they still get outings like this one?
Aboard HMS Obdurate. The trip was from Portsmouth to Harwich. Some of the boys shown clambering on the gun turret are the sons of naval officers from the Royal Naval College who hadn't earned their passage!