direct to your inboxA national lockdown is needed to curb the latest strain of the coronavirus, scientists have warned.Boris Johnson is facing increasing pressure to take tougher measures after the new fast-spreading variant was identified.It comes as more than 40 countries have banned arrivals from the UK over concerns about the virus strain, which is up to 70pc more infectious.Tier 4 measures, similar to the rules in the November lockdown, have been introduced in parts of London and the South East.But in a briefing on Monday, scientists warned the government needed to go even further to mitigate the growing threat.