How is MI5 different to MI6, what do they stand for and what do the spy agencies do?
Both agencies, dating back to the World War One, are tasked with protecting the country but their remits differ
THE agencies widely associated with fictional super spy James Bond both serve the same purpose - gathering intelligence.
But the secretive and highly-skilled organisations have very different remits, as SunOnline explains.
What does MI5 do and what are its limitations?
MI5 is widely understood to focus its intelligence efforts inside the UK but that isn't always the case.
With threats to Britain's security often coming from abroad, the agency says it does "work outside the UK where it’s necessary to protect the UK's national security or to counter security threats".
It describes itself as a "publicly accountable civilian intelligence organisation", not a "secret police force", as it does not have the power to arrest people.
Reporting to the Home Office, it was formed in 1909 under British army captain Vernon Kell to identify and counteract German spies in the country, according to the .
What does MI6 do?
The Secret Intelligence Service, commonly referred to as MI6, works on suppressing and countering threats from abroad.
Its roles include counter-terrorism, counter-proliferation, providing cyber security intelligence and disrupting terrorism and other criminal activities overseas.
It is known to have been active in the Balkans and Libya, where it was reported to have been instrumental in capturing Saif al-Islam Gaddafi, son of the Libyan leader Muammar.
In November 2006, MI6 allowed two officers - a man and woman - to take part in an interview for the first time, where they alluded to the existence of a 'Q' figure on BBC Radio 1.
What does MI5 and MI6 stand for?
The name MI5 dates back to the First World War when it was the fifth branch of the Directorate of Military Intelligence of the War Office - now the Ministry of Defence.
The other "MI" (Military Intelligence) branches were later discontinued or absorbed into other organisations, .
MI5 was renamed to the Security Service in 1931 when it merged with Scotland Yard's Special Section, which had similar responsibilities.
Read about the threats facing our country
From 1909 and throughout the war, MI6 had several names including the "Foreign Intelligence Service", the "Secret Service" and the "Special Intelligence Service".
Its official origins go back to the start of the Second World War when it was adopted as a "flag of convenience", .
It adds: "Although 'MI6' officially fell into disuse years ago, many writers and journalists continue to use it to describe SIS."