CCTV footage showing the last captured images of a "brilliant" young academic before he was fatally stabbed in a "senseless" attack have been released as police continue to hunt for his killer.
Daniel Young, 30, was on his way to work at Coventry University's London campus on January 19 when he was attacked as he used a popular commuter short-cut in Morden, south London.
His murder may be linked to an earlier, non-fatal stabbing of a 23-year-old man 1.5 miles away in Mitcham.
The clip shows the teaching fellow, dressed in a suit and carrying his laptop and a bag over his shoulder, walking along Dorset Road towards the entrance of Kendor Gardens.
He walked into the park at around 8am, and was stabbed within minutes. The first 999 call was made at 8.07am, Scotland Yard said.
Appealing for witnesses a week after Daniel's death, Detective Chief Inspector Cliff Lyons said: "Exactly a week ago today, Daniel left home to go to work.
"He had no reason to suspect he was going to be attacked and there is still no clear motive, or reason, for what appears to be the senseless murder of a brilliant young man.
"I believe his attacker left the park immediately after he attacked him and did so via the Dorset Road entrance. I am appealing for anyone who was nearby and saw something, however insignificant it may seem, to contact the incident room.
"The response from the public so far has been incredibly helpful and both I, and Daniel's family, are very grateful. However, we still need anyone who was in the vicinity of Kendor Gardens and Dorset Road at that time of day to get in touch."
The detective appealed for anyone who might have captured video footage, for example on a cycling helmet camera, private CCTV or a camera on a car, to get in touch.
Officers are sifting through CCTV and are carrying out house-to-house inquiries, both around the park and in the area between the two attacks.
Detective Superintendent Paul Monk said so far there is no description of Daniel's killer, or the suspect in the first attack, but that the investigation has made "significant strides" within a week.
He said: "It was commuter time, it was rush hour. We know that there would have been people close by, and people came to Daniel's aid very quickly.
"I'm keen to speak to anybody who was in the area at that time, particularly in the vicinity of Kendor Gardens and Dorset Road."
So far two men have been arrested. A 26-year-old was held on January 19 on suspicion of murder and wasting police time, and bailed until early March. A 35-year-old was arrested on January 21 on suspicion of murder and was bailed until late February.
Anyone with information can call police on 020 8721 4961 or Crimestoppers anonymously on 0800 555 111.