A QR [Quick Response] Code is a barcode that can be scanned using a camera phone – technology that allows people to access a website relating to a product or service advertised on a poster, for example.

The Glasgow Subway has a free-to-use wi-fi system, enabling internet connection.

A rise in the use of smartphones was key to the U-turn, as campaigners – including the Royal Photographic Society – protested that an outright ban would be impossible to police.

However, Strathclyde Partnership for Transport (SPT), denies it was concerned over any potential loss of advertising revenue if passengers were unable to photograph QR Codes.

A spokesperson said: ‘This is not the reason why there has been a decision by the organisation [SPT] that we recommend we don’t ban photography.

‘No advertiser has said that if you ban photography we will no longer advertise with you.’

Meanwhile, more details have emerged on why the ban was put forward in the first place.

SPT was advised by transport security officials to consider a photography ban as a direct result of the terrorist attack on Glasgow Airport in 2007 and the London Tube bombings of 2005, according to one insider.

In a statement, SPT said: ‘We recognise that the initial proposals were written at a time when there were real concerns over transport security but [we] did not predict the huge uptake in social media and availability of handheld devices with a built-in camera, which many of our customers use.’

However, a final decision on whether the proposed ban on photography will be overturned will not be made until the end of the summer.

The new byelaws will be discussed when the SPT board meets with 12 local authorities in August.

The SPT adds: ‘Responsible photography is something we continue to welcome and we will be revising our conditions of carriage to reflect that.’