Four tenants: one claimant

Four tenants have jointly paid a deposit for a residential property and one of them only has brought a claim against the landlord for its return at the end of the tenancy. Must the other three be joined as co-claimants and, if so, what happens if one or more of them has disappeared or is/are unwilling to litigate?

It is open to any one of the tenants to singularly bring the claim and then, if money was recovered in that claim, the lone claimant would be obliged to account to the co-tenants for their shares. The landlord would have a good defence to any claim subsequently brought against them by any of the co-tenants arising out of the same cause of action. Nevertheless, it is not inconceivable that the court might direct that the co-tenants be given an opportunity to be joined to the claim if it has material before it which suggests that the co-tenants might not receive their due share of the fruits of the litigation, particularly if the lone claimant is