A cursory glance through my stats for the number of
days with hail in March and April this year, suggests
that the figure of 12 is a 2-month record for Romsey.
More of the stuff, 5mm in diameter and opaque, has
fallen in the last hour:

SYNOP 30/1350Z
03/// 41470 72210 10093 20069 49905 52025 72782
85962 333 81710 82915 84650 85072 93205=

METAR
EG// 301350Z 22010KT 9999 FEW010 FEW015CB
SCT050 BKN220 09/07 Q//// BLU=

Details:
wind... SW, force 3.
visibility... 20km.
weather... recent hail shower.
clouds... 1/8 ST, 2/8 CB cap moving away NE,
2/8 CU, 4/8 SC, 3/8 AC cugen, 5/8 CI.
dry bulb... +9.3C.
dewpoint... +6.9C.
RH... 85%.
sea level pressure... 990.5mb (rising).
rainfall last hour... 0.2mm.

beaufort letters (1250-1350Z)... cjp,cpho,cjp,cpro,c.

Nigel (Romsey, Hampshire)