It appears that Mrs Mysterious has already arrived to London...

Dalek kidnapped, further instructions from The Doctor demanded: "A 5'-high original Dalek has been stolen from a British tourist museum. The next day, the kidnappers left the Dalek's amputated plunger and this ransom note on the museum's doorstep, in which they demanded further instructions from the Doctor. Best kicker ever: 'Former Dr Who actor Colin Baker has been in touch with staff at the attraction, and may be asked to send a message to the kidnappers.' Link (Thanks, Rupauk!)"

I mean, seriously, who the hell does stuff like this :)