The essential work to replace the bridge will start at 00:10 on Saturday 4 May and finish at 05:10 on Tuesday 7 May; during that time the railway line between Newbury and Westbury in Wiltshire will be closed.

The bridge, which carries the railway line over the River Kennet, needs to be replaced because of its age and once replaced it will mean fewer speed restrictions will need to be put in place and fewer delays will be caused.

The project to replace the structure is slightly unusual, as the main parts of the bridge deck are being built on site. Owing to the proximity of the River Kennet, a specially made pontoon has also been built, creating more space to safely manoeuvre parts of the structure into place.

The bridge will be erected with the help of a giant crane, which has enough power to lift over 160 elephants into the air at once. This heavy-duty crane will be put together at the site with the help of a smaller crane, a sixth of its size.

Once the large crane has been put together it will be used to lift four sections of the bridge into place to make up the main stretch of the bridge, which is 40 metres in length. Each of the four parts weighs 105 tonnes and will be made from 50 tonnes of concrete reinforced with steel sections.

Network Rail’s project manager for the scheme Jon Turton said: “This work is vital to ensure that the bridge will be fit for purpose for decades to come and allows trains to remain at a consistent speed without the need to slow down which would lead to an increase in journey times.

“We know that the railway is 50% quieter during bank holidays and have planned for this project to take place during the early May bank holiday so that it can be completed with minimal disruption to passengers.

“We would like to thank passengers for their patience during this essential work.”

GWR director of operations Rob Mullen said: “This essential bridge replacement work will allow us to continue to operate services through the area, ensuring we can make the most of our new Intercity Express Trains and in the near future deliver more frequent and quicker journeys.”

Journeys on this route between Saturday 4 May and the morning of Tuesday 7 May will be affected to allow for this work to take place, therefore passengers are advised to check before travelling. Replacement bus services will be available for passengers travelling between Newbury and Bedwyn, and between Pewsey and Swindon.

Trains between London Paddington and Devon and Cornwall will be diverted to avoid the affected stretch of line, which will add up to 50 minutes to journey times. To allow for this, departure times will be amended.

Passengers can find out about any changes to their journeys by logging on to the National Rail Enquiries website http://www.nationalrail.co.uk/ or by visiting the GWR page https://www.gwr.com/travel-updates/planned-engineering.

Updates will also be available on Twitter by using the hashtag #MayBHworks.