I think I read from Gucci website before, this bag is exclusive to London Flagship store, to celebrate the newly renovated London flagship boutique located at 18 Sloane Street. It is called Sloaney Bag.
More from the website.
The limited edition 'Sloaney Bag' collection
With a touch of irony, Frida Giannini has designed the exclusive limited edition 'Sloaney Bag' collection as a tribute to London in the Seventies, when Sid Vicious and the Sloane Ranger came together to define a great British era. For the rock ‘n roll rebellious types there is the Joy GG canvas 'Sloaney Bag' ( available in three sizes ), which bears the Union Jack in all of its glory. While for the more mild mannered and luxury conscious there is the precious Royal Blue Joy edition in either Guccissima leather or crocodile adorned with a gold embossed coronet tag. The Sloaney collection is completed by a luggage set, trolley suitcase, duffle and other travel accessories. The collection will be
only available for purchase at the Gucci Sloane Street store.
http://www.gucci.com/uk/uk-english/gucci-news/sloane-st/