"I'm conscious as the days have gone by that people will want to know how long we're expecting them to keep it up," he told his daily press conference in No 10.

"I think, looking at it all, that we can turn the tide within the next 12 weeks and I'm absolutely confident that we can send coronavirus packing in this country.

"But only if we all take the steps that we've outlined, that is vital, that's how we're going to reduce the peak and once we've achieved that and I think that we will, if we take the steps I've said, then the scientific progress that we've been making will really start coming into play."

Prime Minister Boris Johnson said he believed we can turn the tide against the virus. Picture: Leon Neal - WPA Pool/Getty Images

Mr Johnson thanked the public for the "huge efforts" they have taken in complying with the advice for the battle against Covid-19."We're asking students to put their education on hold, we're asking people not to socialise in the normal way and already we can see the impact this is having on the UK economy and on business, on great, great companies," he said."So it's vital that we in Government stand behind them when what we are asking everyone to do is so crucial for saving literally thousands of lives by fighting this virus."

Mr Johnson said: "UK experts, scientists, expect to start trials for the first vaccine within a month. And above all we're getting better at testing."He added: "To give you an idea of what is coming down the track, we're in negotiations today to buy a so-called antibody test, as simple as a pregnancy test which can tell whether you have had the disease and it's early days, but if it works as its proponents claim, then we will buy literally hundreds of thousands of these kits as soon as practicable."Because obviously it has the potential to be a total gamechanger."Mr Johnson said: "By the same token we're massively increasing the testing to see whether you have it now and ramping up daily testing from 5,000 a day, to 10,000 to 25,000 and then up at 250,000."

Mr Johnson added: "That knowledge of where the virus is will make a huge difference to our management of the disease and our ability to reduce disruption and economic difficulty."He said: "It's by this combination of ruthless, determined, collective action and scientific progress that we're already seeing that we will succeed."And I know how difficult it may be or it may seem right now, but if we do this together, we will save as I say many, many thousands of lives."Mr Johnson said: "I say to business, stand by your employees, stand by your workers, because we will stand by you."

Chief medical officer Professor Chris Whitty warned there will be a "lag" before the public's efforts to stem the spread of Covid-19 will result in a slowing of case numbers."At the moment London from the coronavirus is under pressure but indirectly, but that's going to go up," he said."The first thing that will get under the greatest pressure will be intensive care and respiratory care system, that's the first point of real pressure on the NHS that's going to be happen."And to be clear: even if everybody does all the things we hope and really, really would ask that they will do, the numbers will continue to go up over the next two weeks because there's a lag until things start to improve."

Prof Whitty warned there will be a "global issue" in the supply of personal protective equipment (PPE) as he said NHS colleagues were right to complain they are facing shortages.

"I completely understand the points that my colleagues in the NHS are concerned about on PPE, they write to me regularly about this and entirely reasonably," he said.

"This is a major strand of work for much of the Department of Health and Social Care.

"In the short term this is about making sure the PPE stocks that there are go to the right places, in the longer term ... there will be a global issue we need to put together," he added, noting stocks are dwindling in some countries.

Boris Johnson said the Government stood ready to take further action in London if people did not follow the Government's advice on social distancing, although he ruled out closing down public transport.

"If we feel that it isn't working and we need to bring forward tougher measure, nothing is ruled out," he said.

"It is vital that people follow that advice. There is huge evidence that they are (social distancing) in the takings of the retail sector, the hospitality sector, TfL (Transport of London) in inner London down about 50%, in outer London 60%, but some evidence that in parts of the capital it is very patchy and some areas where people aren't following it in quite the way we need them to do," he said.

He acknowledged there had been some "misunderstanding" over the Government's plans.

"There is no prospect of us wanting to stop public transport in London or stop the Tube or the buses," he said.

"We are going to want people to avoid gatherings where they transmit the disease. If it becomes necessary to do more to ensure that, we will certainly do so."

Mr Johnson said: "On mass buying and the price issue, I really hope that retailers will continue to be reasonable. I certainly wouldn't want to see profiteering of any kind."

He added: "As I said before, we've got good supply chains farm to fork - there's no reason for the shops really to be empty.

"Please be reasonable, please be reasonable in your shopping, be considerate and thoughtful for others as you do it".

Prof Whitty said: "On the antibody tests we should be clear that although we're confident there will be antibody tests, we're not absolutely confident yet about whether the ones that are currently on the market are the right ones and that needs to be tested out.

"And that's something that is an absolute priority for Public Health England.

"But once we have these, the key thing for in the first case health care workers and then other workers and members of society, we'll be able to say to somebody, you've had this virus, you're not likely to get it again at least in the immediate term, and now we can be confident you can return to work and now we can be confident you don't need to be taking some of the precautions you've been taking to date."

He added that "there will be a while before we've actually got this in large enough numbers" and it is "more useful" the further along in the outbreak.

The Prime Minister said future Downing Street press conferences on the pandemic could be conducted "remotely" rather than by bringing journalists into No 10."We may have to find some way of getting them done in a way that doesn't look to everybody else as though we are not following the advice that we give the public," he said."I know that you are all sitting a long way away from each other, but it may be that we need to do more social distancing."

Asked about rising redundancies, Mr Johnson said: "It's very, very important everybody understands that we will stick by businesses and I hope that businesses will stick by their employees."This country is going to bounce back, we're going to need some fantastic companies remaining to bounce back as well and it's absolutely vital that everybody understands that now."On data showing that young people may be worse affected than thought, Professor Chris Whitty added: "Firstly, the great majority of people who get this virus irrespective of age will recover from it and most of them will have a mild or moderate illness not requiring any hospitalisation."He added: "This is a significant issue for everybody. Although the great burden of disease will tend to fall, in terms of severe disease, in the more vulnerable groups, and that's why we've given very specific advice to people who are over 70 or have pre-existing health conditions."There will be people who don't fall into those groups who will fall seriously ill, unfortunately. The great majority will not, but some will."And so we do ask people - take this seriously for yourself as well as taking it seriously for all of society and as a way of taking the pressure off the NHS."

In short:

- Is there any good news?Boris Johnson has said the UK could "turn the tide" of the coronavirus outbreak in the next 12 week if people take the precautionary steps the Government has outlined.- Does that mean progress is being made in developing a vaccine?The PM said UK experts expect to start trials for the first vaccine within a month. He also said the first British patient had been put in a randomised trial for a treatment for coronavirus.- Are there going to be lockdowns to halt the spread?No plans at this stage, despite the "ridiculous" rumours of tanks heading to London. Downing Street said there was "zero prospect" of a ban on travelling in and out of the capital. Irish Health Minister Simon Harris also said he hoped he would never be required to use emergency lockdown powers.- Do young people really have nothing to worry about?England's chief medical officer Professor Chris Whitty has warned the young not to be complacent about social distancing, pointing to cases globally of youngsters ending up in intensive care.- It is all over in China?Not by a long way. No new cases of transmission between people in the country have been reported for the first time since the virus emerged there. But experts are warning that the virus has not gone away in China and new cases have been reported from travellers returning home to the country.- Is it all doom and gloom on the jobs front?Not entirely. The Co-op is creating 5,000 store-based posts to provide temporary employment for hospitality workers who have lost their jobs because of the coronavirus crisis.- Is there any reason for panic buyers to continue their "selfish" behaviour?No, but there never was. Environment Secretary George Eustice told MPs on Thursday that any shortages were temporary and were in fact being caused by the panic buyers. He said "the challenge that we've had is getting food to shelves in time when people have been purchasing more".

In full: the measures discussed by Boris Johnson in his daily coronavirus briefing