Britain can brace itself for an Arctic blast after the first arrival of a Siberian swan which traditionally heralds the official start of winter.

Healthy young Bewick's Swan Gastro arrived in Slimbridge on Sunday - two days earlier than last year's arrival, and almost two weeks earlier than the first Bewick's swan of 2017.

Gastro, thought to be around five years of age, arrived at WWT Slimbridge alongside a previously unknown swan, since named by the researchers as 'Roux'.

The pair were spotted on Sunday having travelled from the near continent overnight on Saturday.

Around 300 Bewick's swans migrate 2,500 miles from Arctic Russia each year to escape the bitter cold - which always follows close behind them.

It marks the start of a celebrated period for the famous reserve which hosts around 30,000 migratory birds every winter.

Staff, who have recorded the Bewick's arrival since 1963, hope there will be an influx of birds over the next few weeks as the mercury dips even further.

Swan researcher Steve Heaven said: "The first arrival of these birds each year is always an exciting time for us at Slimbridge.

"The fact that Gastro is a comparatively young bird and has possibly brought a new mate to join him to overwinter with us is great news.

"Swans usually mate for life, and we hope that Roux could be a potential mate for Gastro, and together they could be the start of an exciting new swan 'dynasty' here at Slimbridge.

"The arrival of the pair, coinciding with the first frost of the autumn at Slimbridge is a clear sign of winter.

"We expect these to be the first of many hundreds of Bewick's and other migratory birds over the coming days and weeks."

Sir Peter Scott, founder of WWT, dedicated much of his time to watching and studying Bewick's swans.

Slimbridge hosts of hundreds of Bewick's swans from late October to early March.

They can be seen on the grassland areas of the reserve during the day and in the evenings they congregate outside the Peng Observatory.

However, fewer Bewick's swans are returning each year.

Recent studies show that since 1995 the number of Bewick's swans making the migration from arctic Russia to northern Europe has plummeted by nearly a half - from 29,000 to just 18,000 recorded in 2010.

Conservation scientists have been studying Bewick's swan for the last fifty years, making it the longest study of any species of bird in the world.

Their research has identified some of the threats that Bewick's face including loss of their wetland habitat, illegal hunting, climate change and hazards in their flight path such as wind turbines and power pylons.

Steve added: "We hope that by giving visitors the chance to see Bewick's swans close-up and in large numbers from our comfortable Peng Observatory that we are inspiring them to help protect this species for future generations."