MI5 have been providing secret training to staff at major retailers such as Asda and Tesco, reports The Independent.
Checkout staff have been told to watch out for people bulk-buying mobile phones, as these could be used as detonators for bomb, and to be alert for people buying large quantities of toiletries that could be used as a the basic ingredients for bombs. Further measures include the use of CCTV in underground car parks that could be the target of a bomb attack.
A Tesco spokesman said:
"We have strict procedures and contingency plans in place and we remain in close contact with the security services at all levels." Asda also confirmed it had "contingency plans" to cover a "number of potential crises".