Wayne Harrison asks:
'I know the exterior shots for Thames House are filmed at the Freemason's Hall in London, but why don't the producers use shots of the real Thames House on Millbank? After all, the producers of the James Bond films are allowed to use the exterior of Vauxhall Cross!'
Hi Wayne. It all comes down to practicalities of filming. Whereas The World is Not Enough was filmed outside MI6's building for a week or so, to get the footage for about a minute of screen time, it takes much longer to film a series like [spooks]. There was no guarantee that the exteriors would be available for the time period available to the production company.

Chez wants to know who created MI5 originally.
MI5 stems from the decision in 1909 to create a British Secret Service to combat German spies. Originally, the service was headed by two men, Captain Vernon Kell of the Army, and Captain Mansfield Cumming of the Royal Navy. Kell's division, known as 'K', handled security within the British Isles, while Cumming's division, C, looked after security threats from abroad. When the whole of the Secret Service was absorbed into the Ministry of Intelligence, K division became MI5 and C division became MI6.

Jamie Campbell asks: 'In Series 2, Episode 6 Danny mentions a MI5 public phone number, 'The Weirdo Line'; is this real and if so what is the number?'
Though I can't say whether or not it's known as 'the Weirdo Line' among real Security Service personnel, there is a number available to members of the public to pass on genuine information relevant to MI5's remit, which is: 020 7930 9000. Information regarding terrorist activity can be passed on via 0800 789321. Please note, these numbers are not to be used for general enquiries or to ask about employment opportunities. Those kind of questions will only be answered by writing to:
The Enquiries Desk
PO Box 3255
London SW1P 1AE

Two related questions, John Bentley asks 'Who played Ellie in the first series? and Katie asks 'Who played Maisie?'
Esther Hall played Ellie Simm, Tom's girlfriend in series 1, and Heather Cave played her daughter, Maisie.

Ben wants to know who writes the series - he particularly liked the episode about the VX Gas.
The series is written by a number of people. The format for the show came from David Wolstencroft, who also wrote the first two episodes of series 1, and episodes 1 and 6 of series 2. He co-wrote the final episode of series 1 with celebrated controversial playwright Howard Brenton, who also wrote episodes 4 and 5 of series 1 and a number of scripts for series 2 - including episode 5's VX Gas story. Simon Mirren wrote series 1, episode 3 and has written again for this year's episodes. Simon played a major part in the background research for the show, including introducing real former spies to the production team. Look out for some new writers in series 2 as well.