Marbrand1:
… they applied for and got the relevant ‘o’ licence and purchased a 7.5t truck.
Hi Marbrand1,
As long as you know that they’ve got the relevant ‘O’ licence (there are a couple of different kinds of ‘O’ licences) for a fact, then you (as an employed driver) are pretty much in the clear in many respects.
When ‘they’ obtained the ‘O’ licence, they had to sign an undertaking that ‘they’ would operate their vehicle(s) legally and safely. If they hadn’t signed the undertaking, then they wouldn’t have been granted the ‘O’ licence. Simples.
Now that you know that… ‘they’ should be referred to that which ‘they’ have already signed, because if ‘they’ think that it’s just some unimportant bit of paper, then we can assure them that the Traffic Commissioner (who granted the ‘O’ licence) sees it VERY differently and will hold them to it. 
If they’re still not sure what to do, then I’d suggest they should re-read what they’ve already signed up for.
Final point… they already have a copy of the undertaking.