The police investigation included Jill's former partners. This included long-term partner Bob Wheaton, a BBC exec, and a brief relationship with Simon Basil, a game warden in S. Africa, who Jill met through the Holiday prog. Both were eliminated from police inquiries. I think police thinking was that Jill's recent engagement may have sparked some jealousy.
According to various press reports Alan Farthing married Maria nee Sweeney during 1990. By all accounts the marriage lasted 7 years until the couple separated. Alan was then introduced to Jill late 1997 by mutual friend Jenny Higham who featured in the recent BBC docu.
At trial AF told the court the marriage had been good but they could not go on living together due to his wife's "personal problems" and that the relationship deteriorated to the degree they separated and were divorced in 1998.
I have not seen any evidence that the police investigation covered the former Mrs Farthing, nee Sweeney, whom I believe is a Catholic of Irish descent.
Very unlikely the former Mrs Farthing was the perp since all witness testimony refers to a male.