LOCOG sold 20,000 tickets to the synchronised swimming events at the Olympic Games despite only having 10,000 available in the second round of ticket sales.

The mistake was down to “human error” when data inputting, a Locog spokesperson said.

Approximately 3,000 people were contacted in the last month and asked if they wanted to exchange tickets.

An email sent out to ticket purchasers said: “Reconciliation of ticket inventory and updates to the seating configuration at the Aquatics Centre mean we can now offer you a chance to exchange your tickets to Synchronised Swimming for tickets to one of the following sports you originally applied for in the initial Olympic ticket application phase.”

One man, who wanted to remain anonymous, said he is very happy with the mistake as Locog have now offered him tickets to the 1500m final.

He said: “Just before Christmas we got an email asking if we could transfer to another sport. We were given the choice of athletics, gymnastics, swimming, diving and volleyball.

“We went for athletics and yesterday found out we have tickets for the 1500m athletics final. I’m really pleased as we wanted athletics in the first place and missed out.”

Nobody from Locog was available for interview but a spokesman said: “As a result of finalising the seating configurations in our venues and reconciling the millions of Olympic and Paralympic ticket orders against the seating plans for around 1,000 sporting sessions, we have discovered an error in seats available in four Synchronised Swimming sessions.

In December we contacted around 3000 customers who had applied for tickets in the four sessions during the second round sales process. We are exchanging their synchronised swimming tickets for tickets in other sports that they originally applied for.”

The tickets being offered to customers will come from the public allocation that was held back to be sold in April this year. It will not come from the sponsor allocations, say Locog.