The Indian coronavirus mutation could "scupper" the UK's march to freedom, a leading scientist has warned, despite the lockdown and vaccine programme leading to cases falling to a seven-month low. "They are a worry".
But the "double mutation" on its own isn't unusual and has been found in other variants.
He was expected to spend four days in the country but Downing Street said the bulk of the work could be done in one day. Being on the red list means people who have been in those countries in the last 10 days can not enter the UK.
A total of 600 people in the Britain have now contracted the coronavirus variant first emerged in South Africa as surge testing is taking place in parts of London over the past few days, new figures showed.
"It might be even less controlled by vaccines than the Brazilian and South African variants".
The virus has been mutating throughout the pandemic.
It is the first time officials have acknowledged the presence of the strain, known as B.1.167, in Britain.
A global mutation tracker on Friday suggested the "double mutant" coronavirus, first identified in Maharashtra, has a cumulative prevalence of 10 per cent in India, a finding that some scientists here said is based on insufficient data and needs more research.
"All variants are starting to be seen across India also".
These are not thought to be key mutations of any of the other variants on Public Health England's list, but have appeared in virus samples before.
According to the health ministry, the new variant could also increase infection rates and easily surpass immune defences.
Dr Simon Clarke, a microbiologist at Reading University, said at the time: 'As for the L452R mutation, we're still waiting for a proper definition of what it does'.
Prof Altmann said he found it "mystifying" and "slightly confounding" that those arriving from India are not subject to a hotel quarantine. PHE and worldwide partners continue to monitor the situation closely.
'We keep it under constant review and we won't hesitate to introduce tougher restrictions and add countries if we think it is necessary'.
"What we are doing is working with India and working with countries around the world to make sure that we increase the proportion of sequencing that is happening around the world but making sure that this is intelligent sequencing so that we can detect where these variants of interest and these variants of concern are", she added.
A staggering 175,910 new cases were diagnosed yesterday, nearly treble the 65,000 cases on April 1.
The Prime Minister had already scaled down his trip to India at the end of April due to the country's worsening coronavirus situation, but Downing Street has insisted it will still go ahead.