Agent Pini Zahavi negotiated a £3m payment for himself from Middlesbrough when he arranged the club's £7.5m purchase of his client player, Yakubu Aiyegbeni, from Portsmouth, in the summer of 2005.

Sources close to the deal say the fee - the largest ever disclosed in English football - is payable by Middlesbrough to Zahavi in instalments over the course of Yakubu's contract, so Zahavi will earn the £3m total only if Yakubu stays at the Riverside for the full five-year term.