There's only two of these in the country - and Manchester has one of them

There’s a rare sight in Manchester, just off the hustle and bustle of Deansgate, which thousands of Mancunians stroll past every day without batting an eyelid.

The rare sight itself is hardly jaw-dropping: It’s a pillar box, like you see all across the land. But this post box is painted a striking shade of sky blue.

And, despite several similar boxes appearing in the last few years, there is only one other pillar box like the Liverpool Road one still on the streets of the UK. The other is directly outside Windsor Castle.

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The sky blue box used to signify a special 'air mail' postal service in the inter-war period, explained Robert Cole, a member of The Letter Box Study Group.

“The post office set up letter boxes in 1862 but in the 1920s this exciting thing came around called an aeroplane,” he said. “They were able to charge more for air mail, so it was an opportunity really.

"They put up special boxes and had special vans that were sky blue and a huge advertising campaign from that time. It was like adverts today for super-fast broadband. It was not that all new post boxes were blue, just some of them in city centre sites and they were special.”

Manchester has one to commemorate this air mail service, introduced by Royal Mail in 1911. However, this isn't its original livery.

The 'type B' pillar box on Liverpool Road, bearing the monogram of George VI started out in life like any other red box, but was repainted in 1983 to commemorate the links between the Post Office and Britain's aviation industry. That was the year the city's Aerospace Museum opened.

This box is the descendant of three other blue air mail boxes Manchester had in