How hard is it for buses not to leave early?

Once again last night, my son missed the early-evening bus to our village because it had left several minutes early. Leaving early is a hassle in a city with a bus every few minutes. In this case, the following bus is nearly five hours later, so it's a big deal.

This particular service is funded by Derbyshire County Council, and I've complained about its early departure before. They appear deaf to the obvious suggestion - that they insist as a condition of their contracts that all drivers are issued with a radio-signal watch or clock that leaves no question as to the exact time. (These cost about £20 each, and some rail companies have issued them to all operating staff for exactly this reason).

Once you have excluded the possibility that a driver has left early because their watch was wrong, you can reasonably get heavy with them through the disciplinary process if they are found to leave early.

How difficult is that? Too difficult for Derbyshire, it seems.