Millions of Britons unable to get close to a television will spend Saturday afternoon watching England’s World Cup quarter-final match livestreamed on to their mobile device – but the time delay means they risk overhearing reactions from neighbours to events they are about to see.

Neil Hall, who leads the product team for BBC Sport, said he expected a record number of people to stream Saturday’s match from the broadcaster’s website but, despite big improvements, most online streaming services still have a significant time delay compared with traditional television broadcasts.

“It’s one of the flaws in an emerging technology,” he said. Streaming viewers are told to expect a lag of at least 20 seconds compared with television output.

During England’s last match, most people were already celebrating England’s penalty shootout victory before those watching livestreams had seen Eric Dier walk up to take his winning kick.

Play Video 1:05 England's historic World Cup penalty shootout win triggers wild celebrations – video

Traditional TV audiences are not yet suffering from streaming – ITV1 attracted a peak of 24 million viewers for Tuesday night’s match and BBC One will be expecting to beat this on Saturday. But there has also been enormous parallel growth in the number of people choosing to watch matches on their mobile phones, especially among younger viewers.

More than 24 million people watch England's penalty shootout win Read more

Before the 2018 quarter-finals, 43.5 million people had already livestreamed a World Cup match on the BBC, more than double the number who watched online matches during the whole of Euro 2016.

“A number of years ago, people accessing streams online had to be in the office on a PC with a fast broadband connection,” said Hall. “Now what we tend to see is around 45% of stream starts are from people on mobile.”

The BBC was working hard to develop technology to improve the situation, he said. “While it can be a factor today it shouldn’t be a considered a constraint for the long term.”

The combination of affordable high-speed 4G internet connections and improvements in streaming technology has made it possible for people to watch football matches surreptitiously in inappropriate situations.

The All England Tennis Club has refused to allow the World Cup matches to be shown at Wimbledon but there is little it can do to stop tennis fans streaming the football. A spokesperson said the club hoped the crowd would show “respect to the players and others around them” and pointed out that mobile phones were required to be switched off inside courts during play.

Couples getting married on Saturday afternoon should be alert for individuals at the back who are staring at a mobile phone in their lap, as should theatre managers: actors in a musical based on Titanic at Nottingham’s Theatre Royal were this week interrupted by the cheers from two women watching England’s penalty win over Colombia from the front row.

Kieran Brown (@Kierbro) Dumbfounded. 2 ladies, 1 older 1 middle aged, slap bang front row clearly watching football on phones during the most poignant moment of lifeboats scene, cheering & giggling like stupid schoolgirls. To say I’m raging is an understatement! They should be marched out in disgrace!😡

Tom Smith, the frontman of the band Editors, was disappointed to be told by organisers they had take to the stage during the match to fulfil a commitment to play a mid-afternoon set during British Summer Time festival in London’s Hyde Park.

“I’m sure loads will have it on on their phones whilst we play,” he said.

People unable to watch the match at home but who do not want to resort to a mobile phone stream are turning to big screens across the UK, with tens of thousands expected to watch in public squares.

However, some councils are struggling to cope with the demand. Manchester has said it will not show World Cup matches on its outdoor screens because it cannot afford the cost of ensuring the events are alcohol-free, following past crowd control issues.