What happens if the airline in question does not have stand-by crew at or anywhere near LGW (in this case)? And the captain's discretion to operate extended hours has lapsed? Must the crew rest and the same crew operate the aircraft once rested?
An aircraft can not be operated without a properly rested crew. If there is no 'rested' crew to operate it then it will have to stay where it is until the appropriate rest period has been reached. For the same crew, this rest period is usually a minimum 12 hours but must be at least as long as the preceding duty period.
These Flight and Duty periods are defined by the Authority responsible for the AOC and Operator themselves but the operators FTLs cannot be less restrictive than the Authority.