A virologist at the University of Leeds has said that the footage of people boarding a busy train from London to Leeds on Saturday night was "worrying" news for the city.
Hundreds of people crammed onto a train from London St Pancras as people fled the capital just hours before it entered Tier 4.
It is thought that a new mutant variant of coronavirus is spreading quickly across London and the South East, with the ability to spread throughout the population up to 70 per cent faster than the original strain of Covid-19.
Health secretary Matt Hancock criticised the "totally irresponsible behaviour", while some people in Leeds fear that the city will soon be put into Tier 4 after an influx of people from the worst-affected regions of the UK.
Professor Nicola Stonehouse, who has spent decades studying viral diseases at the University of Leeds, said that the scenes would still have been disturbing even before the imminent Tier 4 restrictions.
"I don't think that was necessarily worrying because of the new variant, I think it was just worrying generally," she told LeedsLive.
"This new variant still transmits in exactly the same way between people, so any large gathering is extremely worrying. That's the reason why we are all being urged to be very sensible over the next few weeks."
When asked whether people should still visit relatives on Christmas Day, Prof Stonehouse said that everyone should think twice before travelling.
"The government's advice can come across as being very complicated, particularly in areas where the rules have changed several times in the last few weeks," she said. "It is confusing.
"If you don't think it's safe to travel at Christmas, don't do it.
"The bottom line is if you've been self-isolating for 10 days or so, you're probably very safe to go and see somebody else.
"Otherwise, I would say err on the side of caution and don't."
