I've just been checking train ticket prices (with a railcard) for a pre Christmas trip to Edinburgh.
Outward -
HST Dover to St Pancras, any train after 9.00am, then Kings Cross to Edinburgh, £27.40
Return same route -
Leave Edinburgh 9.30, any HST to Dover, £27.40.
Leave Edinburgh 10.30, catch first HST to Ashford, change for slow train to Dover, £27.40
Leave Edinburgh same 10.30 train, wait 30 min at St Pancras for direct HST to Dover, arrive 10 minutes later, £84.50
That's 3 times the price to arrive 10 minutes later - crazy