Tesco has asked Costain to conduct a review of its troubled 拢25m Gerrards Cross project after the dismissal of original contractor Jackson Civil Engineering.

The move follows the collapse on 30 June last year of a 30 m section of the tunnel, which was being constructed by Jackson over a section of the Chiltern railway. The accident disrupted rail services in Buckinghamshire for two months.

Costain, which was originally due to build a supermarket on top of the 拢20.3m tunnel, will now take three months to assess the future of the scheme.

A Costain spokesperson said: "Tesco has appointed a team, comprising Costain and a small number of new subcontractors, to review the Gerrards Cross project before taking a final decision on its future. We will be undertaking surveying, inspection and ancillary work within the site boundary in the near future."

Tesco has appointed Costain and a small number of contractors to review the Gerrards Cross project before taking a final decision on it

Costain spokesperson

Costain added: "The review will allow Costain to fully understand the details of the project to be able to implement the design in a way that restores public confidence in the safety of the project."

The accident happened while a 30 m section of the tunnel was being backfilled. An investigation by tunnel contractor Jackson showed the collapse was caused by overloading. Tesco paid 拢8.5m in compensation to rail passengers travelling between Birmingham and London as a result of the collapse. The commuters had an hour added to their journeys.