Tickets for some of the most popular London 2012 events are to be made available for 20,000 people who were mistakenly told they had tickets.
They will be given an exclusive 24-hour window to buy some of the final million tickets when they go on sale in April.
They were told they had secured tickets during the second round sales, only to learn days later that they had not.
They will be able to choose from sessions such as the opening ceremony and the men's 100m final.
It has yet to be decided if those 20,000 people will be able to buy two or four tickets each.
Tickets will be sold on a first come, first served basis.
A day later the process will be opened up to the 1.2 million people who originally applied for tickets and have so far been unsuccessful.
London 2012's policy will be greeted with delight by the lucky 20,000 and also by many of those who will be entitled to purchase tickets after that first 24-hour period.
However, there will be anger amongst many of those who settled for what they will consider lesser events, unaware that this would deny them the chance to get hold of tickets for the most popular sessions at a later date.
For example, somebody who applied for a number of different events in the first ballot, but was only successful in obtaining tickets to a football match for which there was little demand, has been shut out from the remainder of the ticketing process.
It is only after the remaining tickets have been on sale for a week that those who already have tickets will be able to buy more. By this stage it is likely that there will be tickets only for football remaining.
Those who did not apply at all in the first ballot will also be excluded for the first week of sales.
Ticketmaster, the company which runs the London 2012 ticketing site, has had a number of technical problems since tickets went on sale last April.
The sports on sale will be staggered throughout the week in order to reduce the strain on the website once it has been opened up to the 1.2 million people.
Between five and eight different sports will be made available each day.
No customer will be able to purchase tickets to more than one session.
The Games organisers have come in for heavy criticism for refusing to be more transparent about the ticketing process but insist they will provide a complete breakdown once the process is completed - although they have refused to comment on when this will be.
Games organiser Locog has said 75% of the 8.8 million Olympic tickets would go on general sale to the British public, but it has not clarified how many were made available for showcase events.
More than half of the 1.9 million British people who applied for tickets in the first public ballot opted for the evening athletics session on 5 August, which includes the men's 100m final and the women's 400m final.
More than two million applied for seats at the opening ceremony.
Locog has said some 29,000 tickets out of a total 80,000 (36%) were being made available to the public for these events.
Locog's chief executive, Paul Deighton, has previously said only 30-40% of tickets to the opening ceremony would be sold through the application process, with just as many tickets available at £20.12 as at £2,012.
But with seven million tickets sold so far, such breakdowns have not been provided for other major events, such as the track cycling, for which tickets are highly prized due to a combination of strong British medal prospects and the Velodrome's limited 6,000-seat capacity.