Manchester City boss Pep Guardiola and Manchester United manager Jose Mourinho during the Premier League match at Old Trafford, Manchester, December 2017.

Manchester City boss Pep Guardiola and Manchester United manager Jose Mourinho during the Premier League match at Old Trafford, Manchester, December 2017.

Pep Guardiola and Jose Mourinho stand on the touchline during the Premier League match between Manchester United and Manchester City at Old Trafford, Manchester, December 2017.