The incident took place just before 10pm, with police sealing off the city centre and warning the public to avoid the area.
Armed officers arrived at the scene, in North Street, supported by the hazardous area response team (HART), a group of paramedics who are trained to go into the ‘hot zone’ of incidents from South East Coast Ambulance service.
A man, armed with a knife, was ‘threatening to harm himself’, Sussex Police said, and specialist negotiators were called in to calm the situation down.
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In a statement, a spokesman for the force told The News: ‘The incident was contained and there was no danger to the general public, but police have thanked people for heeding requests to stay away from the area and apologised to the local community for the disruption caused as they dealt with the man.
‘At 1.20am, the incident was brought to a safe conclusion.’
A 45-year-old man from Chichester was arrested on suspicion of affray and possession of a knife in a public place.
He was checked by health professionals before being taken into custody where he remained at 8.50am this morning.