Police are continuing to question a 25-year-old man who was arrested on suspicion of the murder of MP Sir David Amess.
Officers are treating the attack in Leigh-on-Sea as a terror incident which may be linked to Islamist extremism.
Police have searched two addresses in the London area and are not seeking anyone else.
The suspect is said to be a British national with Somali heritage.
Police could hold the man until Tuesday before having to charge or release him.
A candlelit vigil is taking place in Leigh-on Sea this evening to commemorate Sir David’s life.
Earlier Priti Patel has paid tribute to Sir David, calling him a “man of the people” and a “much loved parliamentarian”.
Sir David, who had been an MP since 1983, was stabbed several times during a “very distressing” incident at a constituency surgery in Essex.
Speaking outside Southend police station, the Home Secretary said face-to-face surgeries would continue.
“We will carry on,” she said.
“We live in an open society, a democracy. We cannot be cowed by any individual or any motivation… to stop us from functioning, to serve our elected a democracy.”
