Don't forget that the UK requires both parties to, at the time of meeting at LHR, carry a newspaper, wear a trench coat, and have a secret password, such as
"the birds must be flying to the north this time of year" to which the response is something like "but only in the northern hemisphere". At which time one party checks his/her baggage claim tag number and sees that it matches the number plate (license plate) of the car picking him/her up. Afterward, jump in the car, drive away quickly, and see Boris and Natasha's car chase after you.