Peterborough United have signed Britt Assombalonga for an undisclosed fee with the highly-rated 20-year-old penning a four-year contract at London Road.
Assombalonga, who scored 16 goals during a loan spell at Southend United last term, trained with his new team-mates on Wednesday.
Watford were reluctant to the transfer and have first refusal on any possible transfer.
Assombalonga, who was born in the Democratic Republic of Congo, is expected to go straight into the Posh squad for the opening day fixture with Swindon Town at London Road on Saturday.
Assombalonga scored 11 goals in 16 appearances during a loan spell with Wealdstone and five in five for Braintree making a total of 32 in 67 appearances during his career.
Manager Darren Ferguson said: 'Everyone is aware we have been looking for a striker and this is the one that we have been after. Since Dwight left, we have been after him. We identified him, we have had him watched, he did very well at Southend and Watford thought very highly of him.
'I had a good chat with Gianfranco about him. We thought initially it was going to be a loan, but the chairman has come up with the money and that is fantastic for me. He has once again backed me. It was a position we needed to fill.
'He has a lot of potential the boy, he is strong physically, good pace, good finisher and a really nice lad. He ticks all of the boxes. He has improvement in him, but I don't think people will be too surprised, because it fits our criteria,' Ferguson said. Assombalonga will wear the number 9 shirt for Posh.