It’s 50 years since the diggers moved in to create the largest stretch of open water in the South East.

When work started on the Bewl Water Reservoir at Lamberhurst in 1973, it caused such interest that contractors created a special viewing car park so the public could watch the progress.

Beyond the enormous task of constructing a dam to hold back seven billion gallons of water, three listed buildings that would be covered by the flood had to be dismantled brick by brick and beam by beam and rebuilt elsewhere.

Graham Setterfield, 77, was the deputy engineer on the project back in 1973. He said: “I remember back then during the summer you could jump over the River Bewl.

“I was 26 years old when I started working with a team of around 20 designers, technicians and inspectors, all having backgrounds in civil engineering or similar.

“When there was sufficient daylight, the work was about 18 hours a day, seven days a week.

“There was a lot of local interest from the community.”

“We even built a viewing car park for residents and visitors to watch our progress, and I remember I had one conversation with an animated local vicar who thought the work should be stopped because we were desecrating the countryside.”

Three important listed buildings within the flood area were carefully removed.

The timber-framed Tindalls Cottage – believed to have dated in part from 1625 – is now at the Weald and Downland Open Air Museum in Chichester.

Ketley Cottage was another medieval building saved from the waters. It was rebuilt not too far away at Cousley Wood in East Sussex, where it is now a private home.

Similarly, Grade II* listed Dunsters Mill House – which was even older, being in part from the 14th century – was broken down piece by piece and moved to Three Leg Cross.

Other more modern houses in the valley were less lucky – they were simply demolished.

The reservoir was built to provide enough fresh water for the expanding populations at Medway, Thanet and Hastings.

Construction took two years and cost £11m.

A 30-metre high dam wall, 1,800 metres long, was made using two million cubic metres of clay and sandstone, which were largely dug from the floor of the valley itself.

The bank of the dam was covered in 12 inches of gravel underneath a layer of five-inch concrete slabs to protect it from erosion.

The two large concrete towers are for different purposes. The taller one draws water off from the reservoir. The shorter one is an overflow, designed to prevent the reservoir from getting too full.

The location was chosen because of the presence of clay and the relatively low population in the area.

The lake covers around 800 acres and straddles two counties: Kent and East Sussex.

When full, it is deep enough to cover six London buses stacked on top of each other.

In 2004 additional work was completed on a pipeline connecting Bewl Water with Darwell Reservoir near Robertsbridge.

The 17km long stretch of piping cost £25m and was installed to help resupply East Sussex during times of drought.

Southern Water and South East Water currently share the reservoir to service customers in Kent and East Sussex, and to replenish the River Medway.

Ashley Marshman, of Southern Water, said: “It was a major engineering feat to build such a much loved and integral reservoir.

“It is a testament to the forward-thinking of the time as it is a vital part today of our water resources plan for the area of Kent and East Sussex.”

The reservoir also serves as a major leisure amenity.

There is paddleboarding, sailing and canoeing on the water, and an inflatable softplay aqua park – a kind of floating obstacle course.

Fishing is also a major activity, with motor boats for hire by the anglers.

All around the lake are 800 acres of woodlands that are popular with walkers, cyclists and runners alike, the hardiest of which always attempt to a complete circuit of the lake – a distance of 12.5 miles.

For more information about Bewl’s attractions, visit here.

The reservoir also hosts a visitor centre, conference venue and restaurant by the shoreline. They are run independently of Southern Water by the Markerstudy Group.

The reservoir does not fill naturally.

It is kept topped up by pumping stations at Smallbridge and Yalding, which fill it during the winter with water taken from the River Medway.

During the summer months, when the river level is low, water is returned to the Medway.

A small amount of water is constantly allowed to escape from the bottom of the dam to keep the River Bewl flowing.