It's easy. You just have to not think about the timeline. At all. Ever. Otherwise your head will start to hurt and you'll need to sit down and have a cup of tea.
I'd say if you're writing a story about Patrick you could legitimately
(a) have him do National Service
(b) work out when it would be following normally chronology from the end of Run Away Home and not have him do National Service
or (c) follow AF's own style and set your story in 2007. In which case no National Service.
In my post-RAH story, I chose none of these because I wanted to have the Falklands War play a part so that fixed my timeline.
no subject
I'd say if you're writing a story about Patrick you could legitimately
(a) have him do National Service
(b) work out when it would be following normally chronology from the end of Run Away Home and not have him do National Service
or (c) follow AF's own style and set your story in 2007. In which case no National Service.
In my post-RAH story, I chose none of these because I wanted to have the Falklands War play a part so that fixed my timeline.