Prime Minister Boris Johnson's statement on Monday announcing strict new coronavirus restrictions was watched by more than 27 million, according to overnight figures.
His televised address was seen by 15.4 million viewers on BBC One, while 5.7 million tuned in to ITV and 1.6 million saw it on Channel 4.
An additional 4.4 million watched on the BBC News Channel and Sky News.
That makes it the most watched broadcast for years.
The Channel 4 and ITV ratings include +1 figures. The statement was also streamed on Amazon Prime.
The previous most-watched broadcast in recent years was the London Olympics Closing Ceremony in 2012, viewed by 24.5 million.
People in the UK are now living under strict new measures following the PM's announcement.
They can only leave their homes to buy essential items, exercise once a day, and travel for work where "absolutely necessary" or for any medical need.