In a recent interview with the Radio Times, the BBC director general Tony Hall questioned the future of the watershed.

"The watershed is still a useful way of judging the content and sensitivities, and taste and decency issues," Hall told the magazine.

"But has the watershed got a future in 20 or 30 years' time? I suspect not."

With television viewers increasingly watching content on-demand, it's easy to see why Hall thinks the broadcasting rule could soon become a thing of the past.

But what exactly is the watershed and what does it mean for broadcasters and audiences?

What is the watershed?

The watershed is designed to prevent children from seeing unsuitable material, which Ofcom defines as "everything from sexual content to violence, graphic or distressing imagery and swearing."

When is the watershed?

On free-to-air television, the watershed runs between 9:00pm and 5:30am.

On premium channels, the watershed starts slightly earlier at 8:00pm and ends at 6:00am.

Programmes which contain particularly strong material, such as heavy use of swearing or extreme violence, must be shown later in the evening, to further reduce the chance of the content being seen by children.

Why was it introduced?

The watershed was introduced in the 1964 Television Act, a consolidation of the 1954 and 1963 Television Acts, based on research including the 1958 Television and the Child Report by Professor Hilde Himmelweit at the London School of Economics, which recommended that television channels acted responsibly when scheduling programmes, and recognising that parents couldn't closely monitoring all television viewing before 9:00pm.

Does it work?

Ofcom states that 74% of the general public and 76% of parents believe that 9:00pm is the right time for the watershed, according to biannual consultations with the public.

The regulator takes action against broadcasters who don't adhere to watershed rules, and has found over 350 programmes which breached guidelines since 2004.

In 2010, Ofcom received 2868 complaints that performances by Rihanna and Christina Aguilera on The X Factor final were too raunchy for a pre-watershed audience, however the regulator ruled that the programme had not breached guidelines.

Instead, it recommended that shows such as The X Factor which attract family audiences "should recognise the significant potential for causing offence" and that they should "provide appropriate protection for those audiences".

How does the watershed apply to on-demand programming?

With 67% of 11 to 15 year-olds using smart phones, and 45% of the same age group watching video online, preventing children from watching inappropriate content is a challenge.

Ofcom says it is working with the Government, other regulators and the television industry to protect children using on-demand services.

By Pippa Shawley

@pippashawley