The six-week window to buy London Olympic tickets is set to close at 11.59pm tonight (Tuesday)

The last-minute scramble to get tickets for the Olympics has “hit the roof”, London 2012 chief executive Paul Deighton said.

With the six-week window to apply for the 6.6 million public tickets closing at 11.59pm on April 26, now is the best time for sports fans to try to avoid disappointment, according to Mr Deighton.

He said: “Applications have been steady but at a high level, which is in line with operational expectations - but this week it has hit the roof.

“Every day we have got a massive number of orders, which is not surprising, because people have taken on board that it’s not a first-come, first-served system. They have sat down with their families to decide what they want.

“Since last Friday, we have seen a high level go to a really high level.

“Every day is different, but also in the last week we have been getting three or four times the applications above and beyond what was coming in for the previous five weeks - and the sky’s the limit based on the pattern that I am seeing at the moment.”

There are 650 sessions across 26 sports and 17 days to choose from and people will be limited to a maximum of 20 events each.

The most popular events, including the men’s 100 metres final, have a limit of four tickets per person.

Before sales began on March 15, more than 2.5 million people had signed up to the official website - www.tickets.london2012.com - wanting to go to the Games.

“This wave of sales, in which sports fans will find out whether or not they have secured tickets by June 24, is “the best chance probably by a long long way to get the tickets that you actually want,” Mr Deighton said.

“Anyone who wants to get to the Games should absolutely get their applications done - there is no doubt about that.

“There will be a number of tickets left over. It was always the plan.

“If you are clear about what kind of tickets you desire, apply for them now. You will only regret it if you do not get around to it, and it will be much more difficult if you leave it.”

Prices range from �20 to �2,012. They include paying up to �2,012 for the opening ceremony, up to �725 for the showpiece 100m athletics final and between �50 and �325 for the track cycling finals.

A seat at the opening ceremony is on many people’s wishlist, buying patterns so far suggest. Many fans are also making multiple bids for seats at different events.

“Taking the �20.12p tickets for the opening ceremony, I think we can confidently predict that there will be more orders than availability,” according to Mr Deighton.

Orders have been “pretty well-spread” across the sports, he said, adding: “I think that a lot of people are ordering quite a number of tickets. Families seem to be ordering so they can go together.”

A random automated ballot will kick in for over-subscribed events.

So far, the system has withstood the risk of a technological meltdown. London 2012 chairman Lord Coe has dubbed it the “daddy of all ticketing strategies”.

Mr Deighton believes it is in good shape, even with the pressure of the pending deadline.

He said: “The system has actually worked faultlessly and with a process of this scale and complexity that is extraordinary.

“When things work, nobody really notices and the job my team has done with this system is phenomenal.

“Even though I am expecting we will have significant demand we are confident with the way the system is working and that it can support anything that the ticket buying world can throw at us.”

Mr Deighton noted there was “still an enormous amount to do” once the deadline for the core tickets passes.

The process of matching the demand and the different-priced tickets with the sessions available will then start.

Applications will be processed between May 2011 and June 2011.

Notifications, by email or letter, for those who have been successful, will be sent in June 2011.

London 2012 needs to get 25% of its revenue from ticket sales. It is a vital part of raising �2 billion from the private sector to stage the Games.

Applications for Paralympic Games tickets open on September 9 2011.