Pilot Officer G G Bailey 1940

Hi all,
Can anyone shed any light on why Bailey, Flt Lt Gracie and P/O Himr were detached to RAF Christchurch on 27th October 1940. It seems that they only flew one sortie to intercept an -raid before returning to their Squadron the next day.

BAILEY, G. G. P/O – Joined 257 Sqdn from 5 OTU, 8 September 1940; posted from 257 Sqdn to 43 Sqdn, 10 September 1940; joined 79 Sqdn, 13 September 1940; posted from 79 Sqdn to 56 Sqdn, 15 October 1940; joined 56 Sqdn from 79 Sqdn, 16 October 1940; detached from 56 Sqdn to RAF Christchurch, 27 October 1940 (1755 hrs took off on X-raid with F/Lt Gracie and P/O Himr and landed Christchurch); ceased detachment to Christchurch and returned to 56 Sqdn, 0950 hrs, 28 October 1940

Thanks in advance for any assistance you may be able to offer.
Gerry