Well they 100% would have to approve any sale, as its part of the loan conditions. They could simply repay the loan but the chances of Donald or Campbell having a spare £9m are low. If the loan wasn't being repaid, and Campbell was a dodge pot, you'd hope they'd refuse regardless of whether they want to own us, simply because any massive failure could see them lose out as well
I suspect they would not get involved to that degree unless there was a very specific scenario of them aggressively trying to purchase majority ownership + their bid being close to the one Donald was proposing (and for some reason, Donald not wanting to do it). Even then, exercising a veto based on a charge is pointless because if the other bid was at that stage and Donald wanted to get around it, they could just give him the cash to pay FPP off and they lose the leverage.
Assuming that they're not actively trying to buy us, I'd be staggered if FPP made a subjective judgement about the viability of someone else's bid on our behalf.
From recent experience, we had a relatively similar issue whereby a VC firm invested in us at a low level (6%), who happened to have a mechanism to veto a sale, announced that they were
slightly uncomfortable with us taking money (8 figures a year, so business-defining) from a certain sector because they'd changed their internal fund rules and it was a grey area. The worry was that if we sold in future, they could be difficult and exercise the veto, even if we had no alternative in play and everyone else was in favour of the sale.
In the end through conversations with lawyers and the VC, it was clear that those type of mechanisms are there to protect against the business owner newco-ing the business and essentially ****ing the shareholders (or in FPP's case, a company with loan money outstanding) over through creative ownership changes and transferring assets. The lawyer who dealt with it was extremely blunt and said that for an investor to exercise a veto like that, someone would have to be suffering a massive financial loss and be desperate to do something else with the business.
Just something to be aware of I guess. If FPP aren't actively trying to buy a majority stake, they will probably not get involved and stop someone else doing so.