Garantor looking to pull out of tenancy agreement

[HistoryGeek]

3 of us have just put a deposit down and started renting a flat today, it's a 9 month lease, the only problem is my flatmate's garantor has suddenly had a massive mood swing and is looking to back out. The garantor is his father, and he says he will not let his son move in (his son is 21!) and won't be his garantor. But he's already signed up as his garantor.
Can he do this after signing? Won't he be liable to legal action?

[Eve]

Not if he has signed and the tenancy has already started, he is as contractually bound to the tenancy as the tenants are.

[Twenty20]

If the landlord or agent have done their job properly and he has had sight of the AST agreement so that he knew what he was standing guarantor for then as Jenna says it would be very difficult for him to get out of it, if not impossible. A bit late to back out now!

[themas]

Added to which, unless his guarantee limits his liability to the part of the rent his son is due to pay, he could find he is standing guarantor for the other tenants, even if his son does not move in!