We can prove the disruption happened but not what it cost

The diary is honest and useless at the same time: gang moved off Block B, steel not arrived. It proves the disruption happened. What it does not say is which operatives, for how many hours, doing what instead, and whether the substitute work was productive or make-work. Nobody wrote that down, because everyone was busy being disrupted.

Disruption money is the gap between what the labour should have produced and what it could produce, and that gap has to be measured, not asserted. A tribunal reading the gang was diverted has nothing to price. The half of the record that pays, the hours, the location, the substitute activity, the output, is exactly the half that goes missing, and every month it stays missing the claim gets rebuilt from smaller and smaller scraps.

The capture is not a burden once it is designed: allocation that names hours against locations and activities, diary entries that say to what and for how long, kept as the work happens rather than reconstructed for the claim. Set up on your job, run by your people, and checked monthly so it is still being done in month six.