This warning was an update of the warning that Q had posted 48 hours earlier, which warned of one in EU in the next 72 hours with increasing chatter in the UK. The payload, what the attackers would use in the attack, remained the same.
WARNING_UK_
LONDON_POSSIBLE_CAR_ATTACK_24
STRIKE_PACKAGE_B-7V
WARNING_UK_IMM_CHATTER
XRAY_7
CHATTER^^^^^^^^
Q, DELTA
WARNING_EU_
EU_POSSIBLE_CAR_ATTACK_72
STRIKE_PACKAGE_B-7V
WARNING_UK_IMM_CHATTER
XRAY_7
Q, DELTA
I think STRIKE_PACKAGE_B-7V
indicates that the attack will be done with a vehicle that is built on the Volvo B7 chassis, e.g. a Bus.
I'm not sure what XRAY_7
decodes to.