Fifty swans rescued from a major oil spill in the River Medway have been returned to the waterway after being nursed back to full health.

More than a month ago, on February 11, up to 300 litres of fuel was poured down a manhole drain near Hampstead Lock, Yalding.

The spill affected the River Medway as far down as East Farleigh and was believed to have been the result of the oil being "illegally dumped" near Yalding Station.

The Environment Agency classed it as a category one oil spill - the most serious type - and were concerned how it would affect the waterway's wildlife and ecosystem.

It passed through the Bow Bridge Marina at Wateringbury - where 46 swans and other waterfowl live.

The Swan Sanctuary from Shepperton, Middlesex came to the rescue and escorted all the birds back to safety in what was described as a "mammoth task".

A spokesman from the Environmenrt Agency said: "We identified that up to 300 litres of oil had been fly tipped into a culverted watercourse from a roadside manhole.

"Officers acted quickly to lay a boom across the channel at Hampstead Lock, which successfully contained the majority of the oil.

“Inevitably, some oil was lost downstream beforehand, and this unfortunately impacted the swans, which were later rescued by the Swan Sanctuary and taken away to be cleaned-up."

One month on and the swans are healthy enough to be returned to their home, now cleared of any oil.

Steve Knight, trustee of the swan charity, said: "After we got all of the swans back to our facility they were taken to our oils spill unit.

"We had to wash off all the oil which was a long process as each bird had to be washed individually.

"It took 30 minutes per bird per wash and some of the them had to be washed three times a session."

The oil left some swans needing extra attention as it could cause serious health issues.

Mr Knight said: "Oil coats them and so as they tried to clean themselves and peel it off, they would ingest it, which could cause oil toxicosis which we medicated for.

"They were also checked over twice a week by our vet."

The swans were kept in the facility's oil spill unit and washed everyday until they regained their waterproofing.

They were then then moved to an outdoor water area where they continued their full recovery in comfort.

Now they are healthy and able to return to the Bow Bridge Marina.

Mr Knight said: "It's the nicest part of the job letting them go because it means you have done what you set out to do."

Sue Frankland-Haile, 67, and lease-holder of the marina has praised the charity for their hard work.

She said: "Our thanks goes to everyone at The Swan Sanctuary for all their quick thinking, hard work and amazing care provided to the swans and for their support."

In the face of praise Mr Knight was quick to offer a modest response.

He said: "We don't do it for the praise but for the animals."

The swans have been dearly missed at Hampstead lock. Mrs Frankland-Haile said: "It has been very quiet without them.

"You can imagine how the swans disappearance has been felt by us all in Wateringbury.

"We are all ecstatic that they will be returning in time for them to settle back down before disappearing off once again as they do for the breeding season.

"They have all been missed terribly and the regular visitors that come are delighted that they were all saved from long term damage."

Boaters on the lock, and other members of the community, responded en mass to the news of the swans' return; sending Mrs Frankland-Haile messages of excitement.

Joanna Toch text to say: "We're so happy to be seeing them back and so sorry they went through the trauma they did."

Matt Wickham wrote: "That's brilliant oh at last some nice news! I am pleased as it is really quiet without them."

And Marie O'Connell said: "Wonderful news. The quick response of the Swan Sanctuary as well as the support of so many local people who value and appreciate the wildlife and beauty of that stretch of the upper Medway has resulted in the survival of these lovely birds. Well done to you all and thank you.”

Everyone is excited for the return but two new members of the Bow Bridge family may be less thrilled to see them.

With the swans' absence two new birds have moved into the vicinity and are said to be a dominant pair.

Feathers may fly as a small turf war could break out upon the waterfowl's return.

Mrs Frankland-Haile said: "Since they were rescued, two more dominant swans have entered the area and so it will be interesting to see how they and the previous herd react to one another."

The cause of the spill is still unknown with the Environment Agency saying that investigations are still ongoing.

The spokesman said: "We are grateful for the CCTV footage and information from the public that has already been provided.

"If anyone has any further information that may assist us with our investigation please call our free Incident Line on 0800 80 70 60."

Mrs Frankland-Haile praised their efforts during the clean up process.

She said: "We are all grateful to the EA for their part in ensuring that the river is once again clean enough for them to safely return.

"How we all feel about the people who caused this disaster is another matter entirely!"