Roland Perry wrote:
In message , at 21:58:14 on Sun, 8 Sep
2019, Marland remarked:


It was London Transport which recalculated its route measurements to
Kilometres back in 1972 .
Ironically they chose Ongar as the 0 datum

I think they chose Ongar because it was the furthest east.

which means their measurements start on a line that was closed and is
now no longer theirs

It's not the only disappeared datum. Road miles from London were
measured from the Post Office near St Pauls (the tube station used to be
called "Post Office") because postage was originally calculated by the
mile.



Hmm, I always thought it was where the original Charing Cross was located.

I could see the Post Office might have used its own datum for postage from
its own main London premises for its own purposes but the Post Office
premises you mention were not constructed until the early 19th Century and
many milestones would have been put in place before that by the Turnpike
Trusts who were required to do so.

Perhaps someone else can adjudicate.


GH