Police have released CCTV images of a man they would like to speak to in connection with three incidents at Belsize Park and Hampstead underground stations where members of staff were threatened.

The first incident took place at 6.22pm on July 19 when a man passed through the gates at Belsize Park station without a ticket.

Police said when the man was challenged by a staff member, he became abusive and threatened to stab the employee in the neck before leaving the scene.

On the same day at 7.33pm, a man entered Hampstead station with a second male. The first man appeared intoxicated and pushed through the gate with no ticket.

When challenged by staff, he became abusive and threatened the employee with the champagne bottle he was carrying.

In a third incident on August 12, a man entered Hampstead underground station at 5.24pm without a ticket and was threatening and abusive towards staff when challenged..

Investigating officer, PC Chris Howe, said: “Everyone has a right to work without fear of abuse or attack, and railway station staff are no exception. This behaviour will not be tolerated.

“We are investigating a series of incidents in which members of staff were threatened and I would like to hear from anyone who recognises the man shown in the CCTV images, as he may have information which could help with the investigation.

If you know the man pictured or have any further information which could help the investigation, contact police on 0800 405040 or text 61016, quoting reference 158 14/10/16.

Information can also be passed anonymously to Crimestoppers on 0800 555 111.