Ok then....
Oxford St, London to Princes St, Edinburgh:
Oxford Circus tube - Heathrow T3 tube: 1:08 hrs
Walk to check-in desk: 0:10
Check-in time: 0:30
Flight time: 1:30
Get off plane and out of airport: 0:15
Taxi to Princes St: 0:30
=
Total time: 4:03
QUOTE]
Like I said heathrow express - 15 minutes, Preprinted boarding voucher 0 minutes, airports transit 10 minutes pre board 20 minutes flight 1 hour 15 walk to car 5 minutes into town 17 minutes total 2 hrs. 30 max.
NB most trains take at least 4 hours 45. so it's still twice the length of time.
Another example:
Office to Leeds railway station 45 minutes, train to edinburgh 3 hours 20 mins. 20 minutes to destination - 4 and a half hours.
Taxi to Leeds Bradford airport 20 minutes (no loony everything-but-buses-total-exclusion-zone to circumvent) Through airport 20 minutes flight 48 minutes car at other end 17 minutes - under 2 hours - no contest.
Edinburgh to Southampton - car to airport half an hour from just about anywhere, airport transit 20 minutesflight 1 hour 30 taxi 15 minutes - By train all day.
Internal airlinks have hugely benefitted travel for all sorts of purposes and any attempt to cripple such travel is just London centric Little Enger-lander-ism.