The message
from Roland Perry contains these words:

IIRC its 600 miles as the crow flies.

Around that but it would be more likely to be a seagull than a crow.
About half the direct line distance is over sea.

Worse than that... only 210 miles is over land (200 from Stranraer to
Elgin, plus the last 10 miles).

Can't see how you get Stranraer on the line. AFAICT the half way point
is somewhere near the centre of the Isle of Man and a more careful check
of the split than my first attempt puts the land element at 250, my line
going overland in Cornwall (marginal), Pembroke (St David's head) and
IOM.

--
Roger Chapman