Time hasn't been kind to phone boxes. The mobile revolution has left most standing idle, relics of a bygone era.

But four classic red boxes in the heart of Birmingham's commercial district could have a bright new future amid plans to ring the changes and turn them into small business units.

Brighton-based charitable trust Thinking Outside the Box has been granted planning permission to bring the kiosks, next to Birmingham Council House in Eden Place, back to life.

The trust has already launched similar ventures in Brighton (below) and Plymouth which have seen the small units become coffee outlets or ice-cream parlours.

The proposal does not involve any building work as such but would see the insides of the boxes stripped out and security measures such as locks and vandal-proof windows installed.

Brighton architect Miles Broe has been working with Thinking Outside the Box on the charity's projects.

Six great places for coffee in Birmingham

He told the Post : "We don't know at this stage what the boxes in Birmingham could become as each one of the various uses depends on their locations.

"For example, we have an application to build a shoe-shine kiosk in Westminster as it's a different kind of footfall there.

"A lot of commuters pass by the Birmingham location so I would expect some kind of refreshment to be on sale but we will need to discuss this in due course with the operators.

"I don't think being outside Starbucks will be an issue as some people want to sit down with a cake while others will want to grab a coffee quickly as they go past."

The iconic red 'K6' (kiosk number six) phone box was designed by Sir Giles Gilbert Scott to commemorate the Silver Jubilee of the coronation of King George in 1935.

It was installed across Britain but due to the ever-growing popularity of mobile phones, more and more of the boxes have been defunct and surplus to BT's requirements.

Despite their usage being on the wane, their popularity remains high, especially among tourists, and a whole industry has developed around restoration and also building replicas.

BT runs a scheme called Adopt a Kiosk where people can adopt a phone box for as little as £1 and bring them back into community use.

It is believed more than 2,000 have been adapted nationwide for a variety of uses.

Mr Broe described the boxes as "iconic pieces of both engineering and architecture" and said the aim of the project was to redefine their usage to suit modern-day needs without compromising their appearance on the street scene.

A mobile phone app has also been set up on which customers can order drinks and a donation is made to Thinking Outside the Box to help them with future projects.

He added: "We've got 500 phone boxes in the development pipeline and most towns and cities are interested as it provides a function and is an improvement on them sitting there unused.

"BT is delighted because we're taking away the maintenance issue for unused boxes, many of which just get vandalised, and the company has something like 9,500 so we're saving them thousands of pounds in maintenance. Only around 25 per cent of that figure are now in use as phone boxes."