Boris Johnson is to address the UK tonight in an urgent briefing as fears grow of even tougher lockdown restrictions.The Prime Minister is expected to urge Brits once again to stick to the rules days after the UK topped 100,000 deaths from coronavirus.He will be joined by the Chief Scientific Advisor Patrick Vallance and Chief Medical Officer, Chris Whitty.Stricter measures than the nation's current lockdown are reportedly being considered.London Mayor Sadiq Khan is among those calling for tougher rules such as closing down places of worship and requiring masks to be worn in public at all times.It's been confirmed that one of two Brazilian coronavirus variants was detected in the UK ahead of ministers banning the arrival of travellers from.