Since the beginning of the pandemic, FactCheck has been probing the UK government on key aspects of its coronavirus strategy.

But there are important questions that government departments simply won’t answer in full, despite repeated requests from @FactCheck and others.

Why are some areas facing tougher restrictions?

We all know that the government has shifted to a strategy of adjusting restrictions locally.

But why have so many urban areas in the north of England been asked to move to higher Covid alert levels recently, with more restrictions on how people can work and socialize?

We know that the infection rate – the number of cases in a given area, usually calculated per 100,000 people – isn’t enough to trigger a local lockdown by itself, partly because a rise in cases could reflect more local testing.

The Department of Health has told us that it looks at a range of other factors including the number of patients in hospital, data from GPs and other surveillance programmes designed to measure levels of infection in the community.

But we don’t know which of these is considered the most important, or what the precise formula the authorities use when deciding that one area must move into a higher tier of restrictions when a neighbouring one does not.

What do you have to do to get out of a local lockdown?

This is the question more than 50 Conservative MPs, many representing constituencies in northern England, have asked in a letter to Boris Johnson today.

At the most recent Prime Minister’s Questions, Mr Johnson said “the simplest and most effective way” for areas to get out of tougher restrictions was to reduce the R number – that’s the estimate of how many healthy people is someone with Covid-19 likely to infect in a given area.

But the Prime Minister immediately conceded that this was not the only measure the authorities look at, saying: “We take a decision based on a number of things including the R—also, of course, rates of infection, rates of admission to hospital and other data.”

On Monday the health secretary, Matt Hancock, was asked the same question and said the government was particularly interested in case rates in the over-60s.

But the full methodology remains a mystery, so there is no way the public can know exactly what numbers their area needs to hit before being taken out of tougher restrictions.

How many people are being tested each day?

The simple question of how many people are being tested for coronavirus each day has proved surprisingly difficult for ministers to answer.

They often talk about “testing capacity” – but this just refers to how many swab samples laboratories say they can turn round.

It doesn’t tell us how well the other bits of the testing system are working.

The Health Secretary, Matt Hancock, and Dido Harding, head of Test and Trace, have offered figures for the number of daily tests when questioned by MPs.

But no government agencies publish these figures, so it’s impossible for us to FactCheck them.

How have extra payments for areas facing tougher restrictions been calculated?

Some urban areas that have been asked to put tougher restrictions in place have been given extra funding by the UK government in recent weeks.

Local leaders in the Liverpool City Region negotiated an emergency fund of £40 million, while Greater Manchester council leaders were given £60 million despite the Mayor of Greater Manchester, Andy Burnham, rejecting this offer.

Ministers have been keen to stress that these payouts are being decided on a “fair” and “proportionate” basis.

The Communities Secretary, Robert Jenrick, has said the slice of money intended to support local businesses works out at around £20 per head.

Is this really fair and proportionate? It’s hard to say because,  unlike other extra funds central government has made available for local councils, the formula used to calculate the final payout has not been made public.

We don’t know, for example, if the government takes into local levels of deprivation as well as population.

How much Oxford vaccine has been ordered?

Of course, we don’t know when, or even if, a successful coronavirus vaccine will be ready for widespread use.

But the government has set out some details of its plans to get enough doses of a vaccine in place as soon as possible, assuming one of the many candidates proves successful. Some important questions remain.

Government sources are still briefing journalists that 100 million doses of a potential vaccine being developed by Oxford University and AstraZeneca have been pre-ordered for use in the UK if the drug is cleared for use.

But recent statements from senior figures suggest the number could be as low as 15 million. What’s the real number? We haven’t had a straight answer yet.