In the first two weeks of September, 200,000 under-nines were tested, according to government's test-and-trace programme. That is nearly three times as many as in the previous fortnight.

Government figures reveal that in England demand for tests increased across all age groups under 40, but was particularly noticeable among the under-20s.

This sharp rise in demand coincided with children returning to school in England. Combined with an increase in cases among young people and lab testing capacity being reached, this put pressure on the system and led to delays in accessing tests.

Only 1% of those children who had a test actually had the virus, compared with 3.5% in older age groups, including adolescents, and people in their 20s and 30s.

Symptoms caused by colds and flu viruses shared around children who hadn't mixed for many months may have been a factor in the increased demand.

As winter approaches, when respiratory viruses are common and the symptoms overlap with coronavirus, even greater demand could be created among younger age groups.

But if children do become infected with the virus, they are at very low risk of becoming severely ill or dying from Covid-19.

What happens if there's a coronavirus outbreak in school?

A school is said to have a coronavirus outbreak if there are two or more confirmed cases within 14 days, or a rise in the number of children off with suspected Covid-19.

If an outbreak is confirmed, a mobile testing unit may be sent. Testing will start with the infected pupil's class, followed by their year group, then the whole school if necessary.