Dear Heeeeennnnnry Crun,
Thanks have found the entry you suggested, but not much help to me as I have no website to up/download to/from, but as you can see India Four Two has provided that link - for which thanks!
As for my fathers involvement with -EBOG - I do not know much - I think he would have been about 19 at the time of the photo (1929) & the SE5A was modified for the Bournemouth air race in 1930 which Dudley Watt could have won easily but apparently he cut inside a pylon & was disqualified! I think the SE5As were also used for 'skywriting'.
My father was apprenticed to Vickers (although he said he was kicked out after 6 months) & then worked for Brooklands Aviation, but I am not sure if he worked for Dudley Watt between. From the photo I have to guess the latter as I have photos of him at other Brooklands Aviation sites.
Not much available on the internet except a couple of Flight Global entries, some on the DW2.
Keith