Bristol City Council has also confirmed a revised completion date of October 2023.

The scheme had an original budget of £48.8m and was due to open last September. It will now cost £106.9m and open three years later.

The council said the revisions follow “a thorough review of the work needed to refurbish and restore the Bristol Beacon for the first time in 60 years, coupled with the discovery of previously unknown major structural issues in the fabric of the building and delays to sites works caused by Covid-19.”

It added: “While it has long been known that the building was in desperate need of refurbishment, the nature of the work required – and the corresponding cost – could not be assessed fully until the building was closed to the public and detailed investigations could be carried out.

“As contractors dismantled the building, a number of unforeseen structural and heritage issues were revealed, including asbestos, hidden arches within the walls and Elizabethan wells in the building’s basement.

“These discoveries, alongside the Covid-19 pandemic, delayed the project and added further cost.”

The council considered mothballing or scrapping the scheme but “both options would cost the council significantly more than completing the refurbishment.”

WIllmott Dixon said: “Willmott Dixon has a strong relationship with Bristol City Council as it transforms the Bristol Beacon into a world-class venue that will be a major contributor of future economic growth in Bristol and the local economy.

“The refurbishment of this historic Victorian-era Grade 2 listed building is extremely complex, with a number of well documented hidden issues that have only become apparent to Willmott Dixon and the council as work has progressed.

“Willmott Dixon has worked with the council in an open, clear and transparent way to discuss and agree the right course of action to remedy the numerous issues that have emerged as the various structural layers have been removed.

“The site team are happy that the right solutions have been implemented to ensure the Bristol Beacon is a high quality, fit for purpose and world-renown facility that will be a popular destination over many decades for generations of Bristolians.”

Marvin Rees, Mayor of Bristol, said: “We now know what secrets the building holds, and while this has meant a higher than expected cost to modernise and re-open the venue, our commitment to Bristol Beacon is so strong that investment remains the best financial and strategic option for the city.

“We now have a detailed, resourced plan that gives certainty for when Bristol Beacon will re-open its doors  providing musicians, artists and cultural organisations from Bristol and beyond with a world class venue to perform in and brings  economic benefits by stimulating Bristol’s night time economy and attracting visitors to the city.”