Nice start and you've got the political pomposity down extremely well.
Just one tiny point COBRA stands for Cabinet Office Briefing Room A, as it''s name sguests it''s held in Downing St not the Palace of Westminster.

This is great - I enjoyed it! Though I'm admittedly impressed at Mycroft's ability to burn down 221B whilst leaving the rest of the house intact...;) Very well-written and intriguing. Can't wait for Series 4 now...

Great start, fantastic writing!

So so so good!