2015 'most difficult year in Merlin's history' after Alton Towers crash

But the group - which also owns attractions such as Legoland, Madame Tussauds and the London Eye - has seen its annual profits edge up. Merlin said it overcame a fall in revenues at its theme parks to post a pre-tax profit rise of 0.3% to £250 million in the year to December 26 compared with a year ago.

It said Alton Towers had a "significant" fall in visitor numbers after the accident on its Smiler ride on June 2, which resulted in the 500-acre theme park in Staffordshire being shut down for four days.

Five people were seriously injured and two women, Leah Washington and Vicky Balch, had legs amputated after the rollercoaster carriage they were riding in collided with an empty carriage on the ride. A subsequent inquiry blamed human error for the accident as staff misunderstood a shutdown message and wrongly restarted the rollercoaster.

Chief executive Nick Varney said: "Despite a challenging year, the business delivered a robust performance in 2015.

"However, 2015 was a difficult year for Merlin following the accident at Alton Towers early in the summer season. The safety of our guests and employees must always come first and we have sought to learn every possible lesson to help ensure there is no repeat of what happened on 2 June."

In his review of the group's performance for the year. MrVarney added: "2015 has without doubt been the most difficult year in Merlin's history.

"The accident at Alton Towers in June and the media coverage around it, led to a significant reversal of the strong momentum we had seen in our UK Resort Theme Parks business and consequent impact on overall company performance. More importantly, people we had a responsibility to safeguard sustained serious injuries and ride safety processes we believed robust on this occasion proved inadequate.

"Our focus since June has therefore necessarily been on ensuring we support those injured in every way we can while putting in place extensive measures to ensure such an accident cannot happen again.

"In addition, we continue to invest in further improvements to both engineering and health and safety across the estate, including additional compliance managers in all our theme parks and a new group engineering function.

"This represents a substantial additional investment on top of our already extensive HSS (health and safety solutions) and engineering infrastructure which we must remember has delivered hundreds of millions of safe ride experiences over many years."

His report also revealed the dominant impact of the Alton Towers accident. In addition to the 'significant' drop in visits to the Staffordshire site throughout the main trading season, "this created a difficult day-visit theme park market across the UK". As a result Thorpe Park, Merlin's other major rides park, also experienced a decline in visitation.

The company tried to limit the fall, refocusing marketing efforts towards younger families and the broader short break appeal of the resort. "However, this had limited effect over the key summer trading period in the face of ongoing media coverage of the incident."

Despite this, the new 125-lodge holiday village at Alton Towers performed broadly in line with company expectations.