A long goodbye for two giants of the Norwich skyline is reaching its conclusion - however, it may not be until 2019 that they no longer loom.

Eastern Daily Press: The gas holder in Gas Hill takes shape in 1894. IMAGE COURTESY OF NORFOLK COUNTY COUNCIL - ENJOY THOUSANDS OF IMAGES OF NORFOLK'S UNIQUE HISTORY AT www.picture.norfolk.gov.ukThe gas holder in Gas Hill takes shape in 1894. IMAGE COURTESY OF NORFOLK COUNTY COUNCIL - ENJOY THOUSANDS OF IMAGES OF NORFOLK'S UNIQUE HISTORY AT www.picture.norfolk.gov.uk (Image: IMAGE COURTESY OF NORFOLK COUNTY COUNCIL - ENJOY THOUSANDS OF IMAGES OF NORFOLK'S UNIQUE HISTORY AT www.picture.norfolk.gov.uk)

The gas holders on Gas Hill in Norwich are among the most immediately recognisable structures in the city area, however in February it was revealed they were due to be demolished.

Work towards this began in July, rendering a bid from a local developer to salvage them futile.

However, the structures still remain very much visible, just as they have been since Victorian times.

Now, the National Grid has revealed the progress of the demolition, which is likely to carry over into the new year.

Eastern Daily Press: Aerial view of Gas Hill, Norwich. Picture: John FieldingAerial view of Gas Hill, Norwich. Picture: John Fielding (Image: John Fielding johnfielding001@gmail.com)

Gareth Taylor, land generation manager for National Grid Property, said: 'We have been on site since July and are making progress to dismantle the two gas holders at our Gas Hill Site.

'The holders are redundant and have not been used for storing gas for several years, so we are focusing on clearing the site so it can be put back into future beneficial use for the community.

'We are currently removing water from the gasholders and expect to begin the more visible work towards the end of the year.

'The programme anticipates that the structures and associated equipment will be fully removed by the end of January 2019.'

Early in the year, John Brunton, director of Brundall-based homebuilders Brunton Building Ltd, launched a last ditch-attempt to salvage the structures and use them as part of a housing development.

However, his bid was too late to save the holders, which he hoped to incorporate in the design of a building.

A spokesman for the National Grid said at the time: 'Unfortunately, by the time Mr Brunton approached us, we already had the permission and the process had already started, so it was not possible for him.

'We explained the situation to him and he was very understanding of it.'

The holders are the last ones standing in the region, with the penultimate one taken down from Cremorne Lane, between Thorpe St Andrew and Trowse, in January 2016.

How it is done

Removing a gas holder is a long and complicated process, which can take several months to execute.

The process begins by preparing the land for the removal by draining any water from the site.

The holders - or gasometers - are made up of a number of elements - a tank, inlet and outlet pipes and interlocking cylinders called lifts.

The tanks are rested in a reservoir of water, which acted as a seal to prevent the gas stored inside from escaping.

Despite the holders having not stored gas for several years, removing the water and any sludge is still a lengthy task, due to low capacity of the pipework.

It is also necessary for the water to be checked for any contamination and correctly disposed.

Once this process has been completed, the metal structures themselves are dismantled in a task not dissimilar to peeling an onion.

This involves blowtorching through the steel at the top rim, before peeling sections back with a grab excavator.