Police tailed the prime suspect, 36, in the murder of teacher Sabina Nessa, 28, for hours before arresting him at 3am in Eastbourne.
The arrest followed a huge police operation in which the suspect’s movements were traced using CCTV and automatic number plate recognition.
Sussex Police said: “The murder of Sabina Nessa in Kidbrooke earlier this month has sent shock waves through our communities. Today, detectives from the Metropolitan Police arrested a man in East Sussex on suspicion of Sabina’s murder. We will be supporting the Met with their investigation and will do all that we can to help them get justice for Sabina’s family and loved ones..”