Publication - London Gazette
Whilst nominally published in London, historically The London Gazette carried information from around the world, wherever the British Empire had an interested and beyond. Therefore, within TRP it is treated as a Non Geographic source of gleanings, within the Great Britain part of the hierarchy of gleanings.
It is still published today, see http://www.london-gazette.co.uk/ and for more information about The London Gazette please see http://www.london-gazette.co.uk/about and its sub-pages.