6hr break rule?

J-BONE:
In ref to it being correct if a driver has to vacate his vehicle and withdraw his card on return to the depot for it to be shunted and speedily reloaded for the next shift, if the driver was forced to take his second break in the canteen would that be acceptable to be written against his infringement letter?

Would he need to do a manual entry or a printout explaining his lack of recorded break

It is perfectly acceptable for him to write whatever he likes on the infringement letter (including writing nothing at all) - it won’t make the slightest bit of difference. The sole purpose of said letter is to notify the driver of the infringement (and also to provide proof that it has been brought to his attention - hence the request to sign and return it).

The correct place to write written explanations is on the chart for the day in question (if on analogue tachos) or on a printout (if on digital tachos). Having said that, the correct way to deal with this would be for the driver to make a manual entry using the manual input facility of the tacho at the start of his next shift.