William Reginald Lybbe Powys-Lybbe with Richard, in Tunbridge Wells in 1884
The reasoning is:
(1) The photo was taken in Tunbridge Wells, to which the family had moved in 1882 or so,
(2) so it cannot be RCLP who was born in 1881,
(3) so it is either of O-MPL or RBLPL and
(4) from the photo on p. 27B it looks strongly like RBLP-L who was born on 5th May 1884.