The otter: return of the elusive movie star
While we were screaming at Beatles, the swinging sixties were dark days for our otters.
At the depths of their decline in the 1970s, healthy populations could only be found in Scottish strongholds beyond the reach of harmful pesticides.
Even before their dramatic population problem, the elusive mammals were rarely glimpsed - but a starring role on the silver screen in 1969 film Ring of Bright Water opened many people's eyes and hearts to the animals.
After decades of dedicated work to clean up our waterways, conservationists recently celebrated their return to every county in England and the chances of spotting an otter have now vastly improved.Road to recovery
The success of Ring of Bright Water worked wonders for a species that until then had been regarded as vermin. Otters were illegally persecuted by fishermen and hunted with specially bred otter hounds. The practice was finally banned in 1981.
Like many other creatures at the top of the food chain, such as peregrines and sparrowhawks, otters suffered very badly from the widespread use of chemical pesticides, such as dieldrin, which drained into streams and rivers and contaminated fish stocks.
But unlike birds of prey, which breed quickly enough to replenish their populations within a couple of decades, the otter's low reproductive rate meant that its recovery was far slower.
Following bans on hunting and harmful chemicals, land management techniques were used to improve the otters' habitat and give them the best chance of survival.
Having virtually disappeared from England by the end of the 1970s, apart from the far north and west, otters can now be found across the country and also throughout much of Wales.
And they are not just confined to rural areas: the mammals are regularly seen in the centre of Newcastle-upon-Tyne, and in other towns and cities.
This is crucial because having a healthy population of a top predator such as the otter shows that the river systems themselves are in a good state.
Otters held on in Scotland in far greater numbers than elsewhere, especially the remote islands of the north and west, benefitting from being able to live in parts of the country where hunting and pesticides posed less of a problem.
By 2007, Scottish Natural Heritage reported that the otter's recovery was complete - three decades after serious falls in numbers, especially in the central and southern parts of Scotland.Otter spotting
Otters have now been found in over 90% of the Scottish sites surveyed, with healthy populations on the Clyde in Glasgow, and also in Aberdeen and Edinburgh.
Today, some of the best places to see otters are around the coasts of Scotland especially Shetland, the Western Isles, and the Moray Firth.
These coastal animals are not sea otters - that is a separate species, found along the west coast of North America - but simply river otters that have discovered that the twice-daily movement of the tides can be very productive if you enjoy a diet of fish.
Further south, the main otter strongholds are the rivers Tyne and Tees in the northeast, the upper reaches of the Severn, and smaller rivers such as the Dart in Devon home to the Tarka Trail, a series of routes inspired by Henry Williamson's 1927 novel, Tarka the Otter.Cautious comeback
Otters may have an extraordinary survival story so far, but they still face threats.
Like many wandering mammals, they often fall victim to collisions with motor vehicles as they cross a road to get from one part of their territory to another. At sea, they are also drowned in crab and lobster traps as they try in vain to get at the contents.
Despite the fact that it has been illegal to kill otters for more than 30 years, there are still occasional calls for a cull of otters, especially when they raid garden ponds to seize valuable koi carp, some of which are worth hundreds or even thousands of pounds.
Places to see otters
Experts also warn that invisible threats in our waterways may still be disturbing the mammals following recent research funded by the Environment Agency that suggested hormone-disrupting chemicals could be linked to reproductive problems.
But overall, Britain's otter population is in remarkable shape, much to the delight of their admirers.
One such fan was Gavin Maxwell, the Scottish naturalist and author of the novel Ring of Bright Water, upon which the film was based.
Set around his home in the tiny village of Sandaig in the Highlands, the book was based on his extraordinary and eccentric life and passionate love of otters.
Maxwell had links to two modern naturalists, both of whom made the pilgrimage to Sandaig. The late Terry Nutkins famously went on to present the BBC series The Really Wild Show; while Sir John Lister-Kaye has set up the Aigas Field Centre for eco-tourism in the Scottish Highlands, and written many bestselling books on natural history.
In the same year as the film release of Ring of Bright Water made him a household name, Gavin Maxwell died of cancer, aged just 55.
But his love of otters lives on - not just in the book and film, but also in the otter's real-life tale of revival.
More scottish wildlife can be seen in Hebrides: Islands on the Edge which continues of BBC One (Scotland), Monday 13 May at 2100 BST and is available on iPlayer.