Hello Jean,
A few more loose cogs for you...............
Harold Ashley Curzon Ponsonby:Birth: March Qu. 1892 Chelsea 1a 371
Harold Ashley C Ponsonby
Marriage: March Qu. 1918 Kensington 1a 419
Harold A C ponsonby
Edith F DadsonSo presumably the Edith Clack marriage in Lewisham was to William Henry Dadson, of which I can only find one contender, birth registered March 1885; West Ashford 2a 829.
I can find one Medal Card for a William H Dadson (Royal Engineers and Machine Gun Corps)
I can follow him through 1891 and 1901, but can't find a death for him between 1909 and 1918 in either the full GRO index or CWGC.
I cannot find H A C Ponsonby on the 1901 so far. I've also checked the Medal Index Cards and WO 364 (Pension Records), but no luck.
More questions than answers again.
Phil
Edit: Harold's MIC is here: http://www.rootschat.com/links/02sm/