Blackwell said: "There was plenty of interest in him and I am surprised Watford turned down a £900,000 bid for him from Wolves in December given their situation.
"One club seriously wanted him but had to get a player out being in a position to get him in, but fortunately, we could do something straight away. He comes straight into the squad to add competition for places with Monty and Quinny, who have performed manfully since losing Speedo, which was a massive loss. Also, quite a few are bordering suspensions and we can't afford to be light in that area.
"John-Joe is strong, six foot and likes to get in the box - he's already scored here this season and has got a few goals to his name. Darius and Brombs, who worked with him at Watford, always raved about him and gave me good background infortmation."