Mayweather at Wembley. It would sell out at maybe £100 aticket on average giving $16 million at the gates alone. Add a 3am fight time to please HBO/Boxoffice/Whoever and the PPV would be huge. It would get around 500k in the uk which is an extra $10-$15 million. So thats around $30 million before the US PPV is even considered.

This makes financial sense as well as helping both fighters to cement a legacy. Mayweather may deny it, but his record needs Cotto/Hatton/Mosley.