Do you know how 150137 came to be in P1? I can't find any trace of anything having been cancelled (or short-formed) in order to provide a unit.
I can't help but think that it would have been worthwhile waiting a few extra minutes and using the unit off the 0923 arrival ex-Blackpool (which should have been a 319) on the delayed 0906. The scheduled next working of the ex-Blackpool, 0930 Wilmslow, would have been better able to stand a 150 (on a Sunday), I'm sure. And if anyone should think I'm in any way anti-Chat Moss, I can tell you, it's my local line.
I've got no idea I'm afraid, the unit was already at Platform 1 when the announcement was made.