Construction workers help assemble the slide around the ArcelorMittel Orbit last month ©Getty Images

Ticket sales for the world’s “longest and tallest tunnel slide” down the ArcelorMittel Orbit Tower in the Queen Elizabeth Olympic Park are “very promising” according to the London Legacy Development Corporation (LLDC) - and the struggling venue is now on course to double its annual visiting figure to reach profitability.

The Orbit tower, which overlooks the main Olympic Stadium, was originally forecast by the LLDC to make a profit of £1.2 million ($1.7 million/€1.5 million), but it has run at a loss while being used primarily as an observation point, losing £520,000 ($750,000/€658,000) in 2014-15.

That has prompted the LLDC to install the additional attraction of the slide, which has been designed by Carsten Holler, jointly responsible for the Tower with Anish Kapoor.

Tickets went on sale from April 26, and the attraction is due to open on June 24.

The £3.5 million ($5 million/€4.4 million) ride will measure 178 metres in length and 76m in height, with the descent taking about 40 seconds.

Ben Fletcher, director of communications at the LLDC, told insidethegames: “The issue is that the original projections were made at the time the Orbit was commissioned in 2010, and they were at too high a level.

“Taken by itself, getting almost 125,000 visitors in the first year of opening was a fantastic achievement for the Orbit.

“That’s why we have invested in the slide.

Anish Kapoor (left) and Carsten Holler in front of the ArcelorMittel Orbit which they jointly designed, and which now has the
Anish Kapoor (left) and Carsten Holler in front of the ArcelorMittel Orbit which they jointly designed, and which now has the "world's longest slide" attached to it ©Getty Images

“Once that is in place we are very confident that we will reach the figure of 200,000 visitors a year, which is what we need to make it profitable.

“And we expect to be able to pay back the cost within five years.

“The signs are very promising.

“In just over a week we have sold many thousands of tickets, and we will be making a major announcement soon.”

Fletcher also believes the Orbit’s long-term fortunes will be boosted now that the main London 2012 stadium is ready to be fully used.

“Having events on at the stadium is a big driver of visitors to the Orbit, but the Stadium has been closed for long periods of time during alterations for the incoming tenants, West Ham United,” he said.

“When the stadium is properly open this year we have a series of concerts planned, a Diamond League athletics meeting, and then West Ham moving in.

"All this will have a dramatic effect on the footfall for the Mittal Tower.”

In the meantime, the London Aquatics Centre is preparing to host the European Aquatic Championships from tomorrow in what will be the last major swimming event before the Rio 2016 Olympics.

Read the full Big Read on the London 2012 legacy here.