According to my mate who works for them, there was an OT agreement in place for the last couple of months whereby drivers and guards were getting extra to work rest days and sundays. While the agreement was in place they didnt struggle to cover work because people were coming in for the extra money. That agreement ran out last week and OT is back to being paid at the normal rate. The weather was good yesterday and WMT staff got paid on Friday, so that's pretty much the reason why there were loads of turns uncovered.
This is nothing to do with the RMT or staff going sick, it's just what happens when TOCs haven't got enough staff to cover the work and rely on OT. Sadly the entire national rail system is run like this.
Simply put, there aren't enough train crew at any TOC. One look at the recruitment thread on here shows you how desperate so many people are to work on the railway but can't get on. It's very sad that it's so hard to get jobs when TOCs blatantly need far more drivers and guards than they actually employ. It's a depressing fact of life that TOCs would rather cancel trains than have people sitting spare.
Edit: a quick internet search shows there was also a rail defect near Birmingham New Street yesterday which can't have helped things.
The first part ref the agreement is indeed correct. There has however been a spike in sickness post agreement (part of the agreement stated that if you went sick during the length of that period you would lose all enhancements earned over the entire period)
There are, on paper, more than enough traincrew, however there may be numbers of non-productive staff, due to medical, safety, union or whatever reasons. There is also still the summer leave roster, so despite the school holidays being over, there will be people who like to take leave outside of these periods.
Rosters will have a percentage of spare turns, and cover turns, that doesn't change. but there's no doubt that TOCS will want more and more out of staff productivity wise, they are private businesses after all. The days of a messroom full of crew drinking tea and playing cards are long gone.
Yes, the railway runs on overtime....but there are rest day working agreements, special OT agreements and so on put in place, which is strange seeing as both unions want to see an end to institutionalised overtime (at least thats what their charters say)
When you have all drivers and some SC's earning the money they are, all overtime is taxed at 40% and then NI on that too, so over half of what you earn is gone before you see it. When you're getting enhancements over and above the norm its worthwhile, when its back to normal rates it makes people think twice! Plus when they've earned what they have over the past month or two, perhaps most think its time for a rest.