There's been a spelling mistake. It looks like it should be Kem
pster
From the CWGC:
Name: KEMPSTER, ERNEST ARTHUR DAVID
Nationality: United Kingdom
Rank: First Officer
Regiment/Service: Air Transport Auxiliary
Age: 44
Date of Death: 29/06/1945
Additional information: Son of Walter James Kempster and Florence Ada Kempster, of Leighton Buzzard, Bedfordshire; husband of Hylda Alice Kempster, of Leighton Buzzard.
Casualty Type: Commonwealth War Dead
Grave/Memorial Reference: 3. K. 22.
Cemetery:
RHEINBERG WAR CEMETERY