About 15 years ago I was running for a club that qualified for the National 12-stage relays. The rules were different then, and it went something along the lines of the top 25 clubs, rather than teams, at the Midland championships qualified. This meant that although Tipton 'B', Birchfield 'B', and probably Coventry Godiva 'B', finished ahead of us we got the last qualifying position. The rule was something of a 'leg-up' for smaller clubs, to prevent talent 'drifting' to the biggest clubs. It wasn't fair, and was changed, so we never qualified again.
At the National's back then it was 4 long legs and 8 short, and as one of the fastest runners in the team I got the last of the long legs - leg 10 I seem to remember. It was a hot and sunny day, and waiting in the start pen I noted that our team was two legs behind the leaders, and one behind most of the other teams, with just four teams on the same leg.
Looking back I would say that was one of the hardest races I ever ran. The sheer pressure of not losing any places, and helping to keep our team from finishing last (success on both counts), meant I had to really flog myself. I recall I had difficulty walking to my car afterwards, I was that exhausted.
Best of luck if you do get called up for the first team, but if you do I think the Llangollen Fell Race PB is out of the question