It's two years since the last pay deal on TubeLines. That deal included a commitment to negotiate the payment of allowances to workers undertaking Protection Master and Site Person In Charge duties.
Two years of tedious waffle later, the company still reckons £600 quid will do, while RMT rightly insists on something more like £1,500.
The union is balloting TubeLines members for industrial action. Everyone should vote yes, and any resultant action should be organised to complement other action on the Underground as far as possible.