A JU88 was seen positioning for attack on another Lancaster. Front and mid upper gunners opened fire. At 0030 hrs rear gunner engaged unidentified enemy aircraft. Hits were observed on starboard engine and enemy aircraft dived steeply through cloud immediately followed by large explosion below the clouds. At 0035 hrs attacked by ME210. Pilot not warned as intercomm was u/s. Damage done to main planes, tail plane, fin and rudder. Both gunners returned fire scoring hits on enemy fuselage. Landed at Woodbridge.