Lt. H. Bennett, RAF, died 21/9/18

All,

Whilst on a visit to one of my company's offices in Cambridge (UK), I came across a grave in a local cemetery for one Lt. H. Bennett, RAF. From memory, I think that the gravestone read;

"Lt. H. Bennett, RAF, formerly 21st Canadian Btn, Died on active service 21 September 1918".

Can anyone shed any light on who this person may have been? Units he served with? Cause of death etc?

Thanks,

Vince