The magnificent setting of Tower Bridge played host last night to 140 VIPs from an East End Pearly Queen to the Dean of St Paul’s Cathedral to launch a new City Visitor Trail App for smartphones.

The app explores London’s famous Square Mile on foot through a series of routes, itineraries, personal commentaries and stories.

It was launched against the backdrop of City views from the West Walkway 140ft above the Thames by guest speaker Loyd Grossman, who chairs the Heritage Alliance.

“Tourism is the fifth largest industry in Britain,” he said. “It is driven by heritage, history and the arts.

“The Trail map and app will open up this historic Square Mile in a new way with walking trails and audio stories.”

There is even a lavatory locator on the app, he pointed out, which alone “makes it worth downloading”!

The ‘Market Mile’ trail recorded on the app by historian Alan Dein has been created in partnership with Tower Hamlets Council to take in Aldgate’s Petticoat Lane.

Other commentaries include Tower Bridge itself recorded by exhibition guide Peter Witowski and the Tower of London by Chief Yeoman Warder Alan Kingshott. There are also trails for Leadenhall Market, The Monument, the Barbican Centre, Museum of London, St Mary-le-Bow, St Dunstan-in-the-East and St Paul’s Cathedral.

The ‘Visitor Trail’ launch was introduced by the City Corporation’s Culture & Heritage chairman, John Scott, as “the most fruitful way to discover the City.”

The app is compatible with iOS 6.0 and Android 4.0+ and available to download from the Google Play iTunes store and the City information centre.