IT will take 216 charges packed with nitroglycerine to bring an era to an end next Sunday when Westbury's cement works chimney is blasted out of existence.

After the detonator is pressed at 7am on Sunday the explosive material will be set off to bring the 122-metre high landmark, which has dominated Westbury’s skyline since 1961, crashing to the ground.

Cuddy Group, which has more than 40 years’ experience in managing site demolitions, is in charge of overseeing the blast on the day and have sub-contracted InDex and SES (Specialist Explosive Services), who between them have vast expertise in drilling and blasting high structures.

But it will be nine-year-old Lily Sargent, of All Saints Crescent, Westbury, in charge of pressing the all-important big red button after winning a drawing competition organised by Tarmac in May.

Lily’s mum, Emma Sargent, said: “Lily’s younger brother, Jacob, keeps referring to the chimney as ‘Lily’s chimney’ every time we drive past it.

“We haven't been able go anywhere without people talking about it – Lily is like a local celebrity.

"We’re all really excited.”

Once Lily, a pupil at Westbury Junior School, has pressed the button on top of the White Horse, the chimney will break at its midpoint halfway through the fall while the bricks in the top half of the chimney continue to crumble.

The rubble from the blast, all 2,100 tonnes of it, will be kept onsite and used as backfill to fill in gaps around the site, including holes in the ground which have formed during the deconstruction of the site.

Richard Green, managing director and explosives expert at IndEx, said: “The chimney will be demolished using proven techniques involving initial pre-weakening via removal of sections of the concrete structure followed by the controlled use of explosives to remove more of the structure to cause collapse by rotation in the desired direction.

“The design of the collapse mechanism follows well-established principles which have been successfully adopted for previous successful demolitions of similar reinforced concrete chimneys.”

Despite the vast amount of debris, it is expected to be contained within a small area and the size of the smoke cloud is also expected be minor.

Jonathan Toyn, senior estates manager at Tarmac, the company which owns the site, said: "This event really will mark the end of an era.

"The cement works have been in Westbury for over 50 years and lots of people see the chimney as an iconic landmark in the local landscape.

"We need to make sure we commemorate such an occasion properly and we have done that by preparing thoroughly and professionally, working closely with our contractors, to make sure it's a safe and enjoyable event."

Wiltshire Police will have a presence on the day to support the safe running of the demolition, working mainly around the safe access areas and road closures.

Deputy Inspector Louis McCoy, who will be there on the day with a small team of officers, said: "This is a one- off event and we are sure it will attract a lot of local attention.

"I would encourage all those attending to ensure that they arrive at the viewing site with plenty of time to spare and please ensure that you follow all the relevant road traffic signs and regulations.

"We are looking forward to this event as it is not something you get to see every day and are pleased to be able to support our local community.”

Network Rail will carry out an inspection of the nearby railway track after the blast to ensure that trains are safe to run when are services are due to commence around 9am.