Always been so. Not a problem. Assuming a tanker is available:
Q1 scrambles to reach the edge of the UKADR 1 hour (transit time) before penetration time.
Tanker scrambles and passes overhead LM 1 hour later and picks up Q2 as they do so.
Q1, having made original intercept, either passes them RTB as they take over the task or plugs and returns north with Q2 if a pair is required.
If the tanker is delayed then Q2 scrambles 1 hour after Q1 to take over the task and hopefully Q1 can meet the tanker before having to RTB, if not then it should arrive to support Q2 before it has to RTB. Meanwhile Q3 will be being generated, if necessary, to scramble 1 hour after Q2.
There were many years post 1982 (all at ASI) and 1990 GWI) when no tankers were available at all - the task was still covered by generating and scrambling more Q aircraft as required.