Because of the time difference between the UK and Japan and South Korea, a large proportion of the population is either at work or school when the games are being transmitted live.
Despite this, the BBC's coverage of England's clash with Argentina on 7 June was watched by almost 12 million viewers, with a massive 83 per cent share, according to overnight Barb figures. This was just short of the number who watched the England versus Sweden game on ITV1.
Universal McCann's head of television, Richard Oliver, said he thought there was a further potential out-of-home audience of about eight million who would have watched the game at work, or at the pub, that would not be measured on Barb.
"If you look at games of similar importance, such as the England v Germany game in Euro 96, there was an audience of 24 million. It is not inconceivable that a similar audience will be following England in this World Cup as we progress through the tournament, he said.
He pointed out this was good news for advertisers for those England games that will be shown on ITV, as they are effectively getting this audience for free.
ITV1's nightly highlights programmes have started to perform well despite the combination of the BBC putting its highlights show out earlier, competition from Big Brother and an unfavourable slot.
England's World Cup fortunes are being closely followed throughout the world, according to research from Initiative Media.
Its report covering the first week of the tournament claimed the England v Sweden game was the most-watched game of the World Cup, with an average rating of 8.7. And 80 per cent of viewers in Peru tuned in to see England play Sweden, which was the highest share in Latin America.