I heard Liam on Radio Four last week.
I wondered at the time, if this was a total 'panic' measure by the production team of PM to get the weather on the air - or if switching to a Met Office forecast (presented by a Met Office forecaster) is the actual back-up proceedure.
But, it's not like there was a serious technical or presenter reason to miss the forecast, it was a case of being too wrapped up with the graphics, and not noticing the clock.
Suspect as it's a one-off, no blood will have been spilt (and the very well thought out 'jokey levels of back-up' sketch the next day, indicates no damaged done), but you can't help but feel that if no forecaster appears in the PM studio by 5.55 in future, a call down to the weather centre will be made - instead of calling Liam off the subs bench over at ITN.
My user name might look like Hatton Cross, but it's pronounced Throatwobbler Mangrove.