The family of a 37-year-old man from Ipswich have said they are "really worried" as he has been missing for more than a week.
Gurbaksh Sually, who also goes by the name Simon, was last seen near London Liverpool Street station at about 7pm on Saturday, November 23.
Mr Sually's family have said that although there has been no confirmed sightings of him, the Met Police has said his phone was active in Ipswich at about 2.30am on Thursday.
His brother Mohinder Sually said his family have been working to try and find him.
He said: "We are all so stressed. We've been into all the bars, pubs and everywhere we can think of in Ipswich, people are being really helpful by putting up flyers and at first it feels positive, but two or three days in and we haven't got anything concrete you start to feel really disheartened and worried.
"It's the worry and the stress of not knowing where he is that is the worst.
"We all really love him and we all really miss him, we just hope that he gets back in touch with someone and lets us know he is okay, or if something serious has happened to him if anyone has any information then please contact the police."
Mr Sually, who works in London for a US-based digital marketing company, was in the capital visiting a friend who recently got engaged.
The chief executive of the company he works for is also heading to the UK next week to help with the search, the family have said.
The missing man has been described as around 5ft 8ins, of slim build, dark black hair which is greying and wears glasses.
Anyone with information is asked to contact the Met Police, quoting the reference number CAD7457/24NOV.
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