"Dogging blocks" have been installed at a national park beauty spot in a bid to stop the late-night sexual encounters.

Locals have welcomed the large concrete barricades, after being plagued by the nocturnal activity for years, but some nature lovers have complained that the measures have ruined the idyllic waterside location.

Llwyn-Onn Reservoir in the Brecon Beacons National Park is recommended on dogging websites.

Couples park up and flash their car lights to attract voyeurs waiting to watch them have sex.

Welsh Water, who own the land, has spent £50,000 blocking up car parks alongside the reservoir and filling them in with tons of chippings.

A spokeswoman said: "We have been carrying out work following complaints regarding anti-social behaviour in the area.

"We have been working closely with local authorities, the community and the police to prevent future incidents at these sites."

The car parks have been used by genuine dog walkers, fishermen and sightseers for generations.