with others, and to stop all unnecessary travel.

We need people to start working from home

where they possibly can.

Coronavirus began as a health crisis

but it has rapidly morphed into a political and national one.

For Boris Johnson this could well

be the biggest test he will face as prime minister.

It's not that long ago that he won that stonking

80-seat majority in December's general election,

where he promised to get Brexit done,

but also level up the country by tackling regional inequalities,

as well as reforming government, and the way things

are done in Westminster.

That has now all gone out of the window,

as everybody behind the doors of 10

Downing Street is entirely focused on how

to deal with this crisis.

Every decision Boris Johnson makes about coronavirus

is going to be a political one.

And every single one will be tested

as he is further scrutinised for the UK's approach to dealing

with this.

And if you ask, well, why are we doing this now?

Why now?

Why not earlier or later?

Why bring in this very draconian measure?

The answer is that we are asking people

to do something that is difficult and disruptive

of their lives.

And the right moment, as we've always said,

is to do it when it is most effective.

Boris Johnson has been under a lot of scrutiny

because the UK has taken a rather different approach

to other European countries such as Ireland, France, and Italy.

Whereas they, very early on, introduced dramatic social

distancing measures, the UK is still

relatively business as normal.

At the beginning of this week, schools were open,

restaurants were serving, and people were still

drinking in pubs.

We're expecting more social distancing measures

to come in, in the coming days.

We have been guided by the science,

and we will do the right thing at the right time.

Boris Johnson has relied on scientific experts

throughout this thing, being posed

with Boris and the boffins, as it's called,

with his chief medical officer on one side,

and the chief scientific officer on the other.

He's been relying on their advice,

and pushing out the more difficult questions to them.

But there's still been some missteps

from Downing Street in this.

The question of herd immunity has troubled Number 10.

It began by briefing to journalists

that this was what the UK was achieving, trying

to get as much of the population immune to coronavirus

as possible.

But as the disease spread more rapidly,

and there were fears the message was backfiring,

they've now had to U-turn on this policy,

with the health secretary saying at the weekend the focus is

on saving lives as much as possible.

We've done what can be done to contain this disease,

and this has brought us valuable time.

But it's now a global pandemic, and the number of cases

will rise sharply.

Indeed, the true number of cases is higher, perhaps much higher,

than the number of cases we have so far confirmed with tests.

Ultimately, this will be a political test

for Boris Johnson.

He's well known to the British public as a jovial sloganeer,

a campaigner through his time as mayor of London,

an MP, and prime minister who is able to inject

a sense of optimism.

But now he has to prove himself that he can govern

in the most testing crisis.

Nobody doubts the coronavirus will be the biggest test facing

British governments in modern political history,

and that is the same for Boris Johnson, too.

Over the next couple of weeks you're

going to see a lot more of the prime minister,

a lot more transparency for the government, as people

will see whether he can step up to this crisis.

So far, the reviews are he's done pretty well

in very testing circumstances.

But the circumstances are only going to become more testing,

and the questions and political decisions

facing Mr Johnson behind this door even more onerous.