I think you will find that BA in their quest to be 'Fit for 5' are trying to make T4 a shambles so that when T5 does open it will all be a pleasant surprise. In doing this, working agreements with the baggage handlers/loaders are being 'tweaked' so that being paid for an 8 hour shift does actually equal 8 hours work. It's a novel concept I know. They (the loaders), unsurprisingly, are not happy and are making sure that their progress unloading aircraft is, shall we say, 'glacial'.
The winter of discontent has begun.