The future structure of England's T20 competition might be in doubt, but there is no doubting the success of NatWest Blast Finals Day.

Tickets for the three-match climax at Edgbaston on Saturday 20 August have now sold out, with the exception of the allocation of 3,200 tickets reserved for the competing semi-finalists.

This is the first time in the history of NatWest T20 Blast Finals Day that the event has sold out before all semi-finalists have been confirmed.

The four teams that will qualify for two semi-finals and a final in a full day of T20 action receive an allocation of only 800 tickets for Finals Day.

Should any of these tickets remain unsold, Edgbaston will release a final allocation at 1000 on Tuesday August 16.

Notts Outlaws and Northamptonshire Steelbacks have already won through following the first two quarter finals. Gloucestershire meet Durham on Wednesday and Glamorgan face Yorkshire on Thursday.

Gareth Roberts, Commercial Director of Warwickshire County Cricket Club, said: "NatWest T20 Blast Finals Day is the biggest day in the domestic cricket calendar and is growing in demand each year, with tickets for this year's event selling out in record time.

"This will be the eighth NatWest T20 Blast Finals that Edgbaston has hosted and is part of our long-term staging agreement, which sees the event played here in Birmingham until at least 2018."

Controversy surrounded the start of the tournament in May when Colin Graves, the ECB chairman, who favours a big-city competirion that would by-pass the 18-team county system, called the present competition "mediocre".

Despite that, attendances have shown a slight improvement this season, following a large leap in 2015, even though there has been additional competition from the European football championships and, latterly, the Olympic Games.