The official emblem of the Houses of Parliament is the portcullis.
It is used on documents, stationery and other parliamentary material and is normally represented in green for the Commons and red for the Lords.
The portcullis can be seen nearly everywhere in the Palace of Westminster - carved into much of the stonework and woodwork and embossed on the leather of many of the chairs.
It is even cast into the metal of the huge bell in Big Ben clocktower.
The Speaker has warned that the use of the portcullis badge to promote an unauthorised or unofficial publication or TV broadcast is a contempt of Parliament.
In 1994 the editor of the Guardian newspaper, Peter Preston, was reprimanded for impersonating the MP Jonathan Aitken by sending a fax on House of Commons notepaper.
Edwina Currie MP was rebuked by the Speaker for using the parliamentary emblem on the front cover of her novel "A Parliamentary Affair" - it is emblazoned on the stockings of a young lady in stilettos.