Birmingham City have been fined £42,500 after a Blues fan attacked Aston Villa captain Jack Grealish last season.

Paul Mitchell ran onto the pitch and hit Grealish from behind during March’s Championship derby between the sides.

Mitchell was jailed for 14 weeks on 11 March.

An independent regulatory commission has also warned Blues about their future conduct, having been found to fail to ensure the supporter conducted himself in an orderly fashion.

The three-person commission was unanimous in its decision, which Birmingham have the right to appeal.

Birmingham, who must also pay the unspecified costs of the commission on top of the fine, argued it did “all due diligence” to control spectators at St Andrew’s for the second city derby.

While the commission acknowledged “the club did many things ‘right’ in preparation”, there were a “number of serious failings” considering the “nature” of the game and “animosity between the clubs”.

It added that they “fell very significantly below standards” of due diligence and placed breaches at the “upper end of the range of seriousness”. It was also stated that “in some respects” Birmingham “was almost cavalier”.

The incident happened after both sets of players had been involved in a melee when Blues midfielder Maikel Kieftenbeld fouled Grealish in the fifth minute of the game.

Both clubs were fined £5,000 by the Football Association on 18 March for failing to control their players.

Mitchell, who was banned from attending any football matches in the UK for 10 years, was himself fined £350, which included £100 compensation for Grealish’s “pain, discomfort and shock”.

The Villa captain went on to score the winner in the derby.