A major rail route across Kent has been shut entirely this week to allow Network Rail access to the track to carry out a £3 million improvement project.

With engineers hard at work making a steep cutting at Selling less prone to landslips, we sent reporter Rhys Griffiths onto the tracks to witness the effort first-hand...

Emerging from the damp, gloomy expanse of the Selling tunnel into the weak winter's sunshine, you are once again reminded of the scale of the Victorian engineering marvel that is Britain's railway network.

Opened in 1860 as part of the London, Chatham and Dover Railway, this line was just one of many which radiated out from the capital during a great boom in building which eventually saw thousands and thousands of miles of track reach all corners of the country.

The modern rail map is testament to the enduring legacy of those early pioneers.

But where their routes remain, they also bring with them historic infrastructure challenges for the men and women tasked with following in their footsteps.

Here on the Southeastern line between Faversham and Dover, closed for eight days this half term for a £3 million maintenance project, it is possible to witness how today's engineers are making Victorian infrastructure fit for the 21st century.

The work site at the western portal of the 401-yard tunnel is deep in a cutting, accessible down a temporary flight of more than 100 metal stairs descending to the track bed below.

Network Rail staff and contractors, kitted out in distinctive orange work gear, can been seen amid numerous pieces of heavy plant machinery which have been brought onto the railway to carry out the work.

They are installing what is known in the construction world as a king post wall, which once complete will hold back the mass of soil which towers over the line.

A huge drill is used to bore a hole in the ground into which concrete is then poured.

Then, sturdy steel beams are inserted an equal spaces, ready for pre-formed concrete panels to be slotted in to build up the barrier itself.

Climate change - in the form of wetter winters and drier summers - is increasing the risk of landslides onto the railway. By carrying out pre-emptive work like this there is reduced chance of future slips which could delay or derail trains.

Tyrone Williams, blockade director at Network Rail, said: "The main part of this particular project is here at Selling tunnel, where we are mitigating the risks from flooding and landslips.

"The structure that we're building here is a 56-metre king post wall renewal. This is to mitigate and control the risk of landslip onto our infrastructure.

"This helps us also mitigate the risk of us putting out emergency speed restrictions on the line."

Network Rail constantly monitors a host of sensors across the network which alert staff if there are signs of movement which could point to a potential landslide.

If detected, this could mean trains are slowed or halted altogether, causing disruption to passengers.

Renewal of the cutting and installation of the new retaining wall will hopefully reduce the need to disrupt the smooth running of the line in future.

Ross Boyle, a communications manager for Network Rail, said: "One of the challenges with earthworks is that the Victorians used materials and methods which we just wouldn't use today.

"While we're in awe of what they achieved, we would do it differently and modern railways do it differently.

"What's exacerbated the challenge with landslips is climate change.

"Wetter winters, significantly wetter winters, and drier summers mean that landslips and difficulties with our earthworks are more common."

Carrying out an eight-day closure of a significant 22-mile stretch of the county's rail network - as opposed to a series of shorter periods of weekend engineering works - is also a decision taken to minimise inconvenience to the travelling public.

Mr Boyle said: "As well as earthworks at six sites along the line we're refurbishing all the stations, deep cleaning and repainting, those really difficult jobs that you can't do when passengers are using a station.

"We're working at a number of structures along the line, again Victorian structures, where the brickwork needs to be repaired.

"Lots of biodiversity works too, we're very conscious that we need to improve our station environments so we're removing invasive species and diseased trees, and replanting with native species and native wild flowers to really give the local environment and local flora and fauna a boost.

"Doing the work in eight consecutive days means we can get it done a lot more quickly, more efficiently, and we can do a lot more.

"Weekend after weekend of works is very disruptive to the passenger.

"So getting it all done in one go is absolutely what we want to do to give them those extra benefits and to reduce the overall disruption to them."

Network Rail regularly comes in for flak from critics who say it is making the risk of landslips worse by removing trees and other vegetation alongside railway lines, but this is something it is keen to refute.

"A common misconception is that trees on a railway cutting help prevent landslips but that's actually untrue," Mr Boyle explained during our visit to the Selling site.

"They increase the likelihood of landslips and what often happens is that we end up with soil and trees on the track."

The work on the line between Faversham and Dover, which includes exploratory works to identify any other sites at risk of landslides, is due to conclude on Saturday.

Thousands of tonnes of earth will be removed from the cutting at Selling to reduce the steepness of the slope.

Rock netting will then be applied to the cutting face to stop loose materials falling onto tracks.

New rail, sleepers and ballast are also being laid, while sections of collapsed drainage on the line will be completely rebuilt to stop flooding delaying trains and damaging track and signalling equipment.

While the route is shut buses replace trains between all stations, so passengers are advised to allow extra time to complete their journeys.