Clive Coleman:
I think it was discovered quite early on and most of the broad gauge
were converted to sleeper type track, on broad gauge.

No, it was just that they stopped having vertical piles. If the GWR
hadn't retained its longitudinal sleepers, they would have had a much
easier time when they finally abandoned the broad gauge in 1892.
As it was, they had to cut all the cross-transoms to allow one rail
*and* its longitudinal sleeper to be moved inward.
--
Mark Brader, Toronto | "This man must be very ignorant, for he answers
| every question he is asked." -- Voltaire

My text in this article is in the public domain.