Boris Johnson to give press conference at 5pm - watch live Ministers consider £500 payment for positive Covid test Boris Johnson suggests lockdown could last until summer Fraser Nelson: Vaccines may usher in Fortress Britain Coronavirus latest news: R-rate falls below 1 across the UK Subscribe to The Telegraph for a month-long free trial Boris Johnson is in for the "mother of all arguments" with his backbenchers now the R rate has dropped below 1 and the UK case rate will begin to fall, a top Government scientific adviser has said. Prof Sir David Spiegelhalter, a Sage academic, said pressure on the Prime Minister would grow as deaths and case numbers fall, while hospitals will remain under significant pressure. The UK's reproduction rate is now estimated to be 0.8-1.0, suggesting a decline in the number of new infections. Last week, it was between 1.2 and 1.3. The rates are lowest in London and the East of England, although still thought to be above one in parts of the North. Tory MPs have already begun calling for lockdown to ease. Sir Desmond Swayne told the Telegraph: “Given that the Government itself has selected and put so much store on the R rate, you would expect there to be some reaction, a payback, a recompense in terms of the lifting or the promise of lifting of restrictions.” He added: “That is why we need some sort of urgency and plan from the Government as to when and how they’ll start restricting decisions.” Some Conservative colleagues suggested that while the R-rate might not be the trigger point, the Prime Minister would be under pressure to give a clear exit plan as cases continue to fall. One former minister said it would be “difficult to justify” lifting restrictions until the pressure on the NHS started to ease. “But we need a plan for getting out,” the senior Tory added. “He needs to show some ankle.” Follow the latest updates below.