Footage of the incident showed the Newsnight political editor being shouted out as he walked through Whitehall, branded a “traitor”, and then chased as he retreated to a safe place away from the crowd.
The incident happened on June 14 last year, during a large protest against the government’s use of emergency Covid restrictions during the pandemic.
Mr Watt was targeted due to his job, and had been picked out because of the BBC lanyard around his neck.
Djazia Chaib-Eddour, 44, Martin Hockridge, 58, Alexander Peat, 34, Christopher Aitken, 62, and Gary Purnell, 45, were all charged with using threatening, abusive, or insulting words or behaviour, with intent to cause harassment, alarm, or distress, and were found guilty at trial.
At Westminster magistrates court on Tuesday, Purnell, Peat and Hockridge were handed 12-month community orders with a requirement to carry out 200 hours of community service. Chaib-Eddour was given a 12-month community order with 100 hours of community service and 20 hours of rehabilitation.
“This was an extremely unpleasant incident in which each of you used abusive words and threatening behaviour towards Mr Watt”, said District Judge Louisa Cieciora.
“This was committed against somebody who was providing a service to the public, even if you did not agree that service was being performed to the standard it should have been.”
The court heard that during the trial Mr Watt was “intimidated” again after giving evidence against the defendants, while the CPS barrister “had to be escorted out of the building by police”, said prosecutor Sudara Weerasena.
Judge Cieciora said she would not hold that against the defendants personally, as they had been in the courtroom at the time it occurred.
In a statement, Mr Watt told how he ran to the gates of Downing Street “as fast as I could” because of the “size and aggression of the crowd”.
“At the time of the incident I was shocked and alarmed at what was happening to me”, he said.
“I felt I was in immense danger.”
Mr Watt said he has been the subject of death threats on “conspiracy theorist forums” and has concerns “my safety can no longer be guaranteed”.
“Whilst not from identified suspects in this case, they were clearly inspired by the incident,” he said.
“My family and I found them very distressing.”
Hockridge, from Harpenden, Herts, Chaib-Eddour, from Hackney, Peat, from Wandsworth, and Purnell, of no fixed address, were ordered to pay a total of £395 in costs and other charges, and they are all banned by indefinite restraining orders from contacting Mr Watt.
An arrest warrant was issued for Aitken, from Lambeth, after he failed to attend the sentencing hearing.
Joseph Olswang, 40, from Richmond-upon-Thames, pleaded guilty over the same incident, and was sentenced in June to 20 weeks imprisonment suspended for 18 months.