A 'bit of a black market' of tickets for the remaining World Cup games is operating in Russia, police said.
Supporters began to arrive in Moscow on Tuesday ahead of the national team's biggest game in decades - a World Cup semi-final against Croatia on Wednesday night.
Police estimate there could be as many as 10,000 England fans jetting into the Russian capital for the game but perhaps only half will have got hold of official tickets.
Interest in travelling to Russia has soared since the beginning of the tournament, which began with historically low numbers of England fans in the stands against Tunisia.
Mark Roberts, National Police Chiefs' Council lead for football policing, said: "I think we'll see more, I think influx is probably overstating it.
"We're estimating eight to 10,000 - it's really difficult to tell because when people take direct routes it's obviously easy to count them but people might come by diverse routes, there are quite a lot of expats here and other fans staying out."
Asked how many might be ticketless, he said: "It's difficult to judge, we know from the ticket sales we can probably reasonably expect through official channels about half that number to get tickets.
"There is a bit of a black market, but not much of one.
"Even though it's not the Russian's team, it's on their doorstep. How often do you get a World Cup semi-final in your city? So there are not a great deal of tickets going spare.
"So there may be people here without tickets, hopefully they can enjoy the atmosphere in the fan fest."
According to the Russian Ministry of Communications, nearly 7,000 more England fans ordered a Fan ID after England's quarter-final win against Sweden on Saturday.
In order to gain a Fan ID, punters need their ticket number to apply for one. Emma Coulthurst of TravelSupermarket told the Times: “The one thing you need to be sure of obtaining is a visa or a Fan ID, the means of getting to Russia without a visa during the World Cup,” she said.
“Many proud fans have been posting their tickets on social media and fans back at home wanting to go have been using the ticket numbers to enable them to get the ID.”
As of July 7, some 21,700 fans had ordered the obligatory identity cards - which in itself was a rise from 17,722 from the day after England beat Panama 6-1.
According to the communication ministry's spokeswoman the number of Fan IDs ordered by England fans stood at 28,048 by Tuesday.
As for tickets, those on the official Fifa website had sold out by Sunday, while the Football Association sold its official allocation of 2,180.