Three men are wanted after a fight broke out between football fans on board a train travelling between Bournemouth and Brockenhurst.
British Transport Police have released images of the men wanted in connection to the incident, which took place on October 5.
The incident came after a match at Bournemouth earlier in the day which Millwall lost 5-2. The Football Association launched an investigation after a missile was thrown at a Bournemouth player, apparently by a Millwall fan, as he celebrated his side's fourth goal.
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The killer's solicitor has written to police challenging them to prove his confession.
Tottenham last won the league back in 1961 - but they are feeling confident after a string of great performances this year so far.
Crimestoppers are offering the reward as police say they are becoming increasingly concerned at the viciousness of the assaults.