undertaker:
Could you argue the assessment drive is an examination so exempt from drivers hours rules??
Not an expert, but assessment drive is still covered by same rules as others.
Would be handy for spme companies if it was as thry could send out a drivers mate and claim “he’s the assessor so out of scope” if stopped. Don’t give them ideas. 
Holidays are usually the best way and as it’ll only show maybe an hour or two on the card, the current lot prob won’t even notice it.