From bbc.co.uk/doctorwho:
Monster maker Neill Gorton has revealed the pain behind his most challenging creation yet - the Racnoss Empress from The Runaway Bride, played by Sarah Parish.
"We've fitted all manner of prosthetics to hoardes of tough stuntmen over the years," said Neill, "but Sarah is, without doubt, the hardiest person we've ever had the pleasure to work with!"
Parish had to endure punishing 14-hour days to become the sinister half-spider, half-human Empress of the Racnoss. This included a full two hours in the prosthetics department each morning of the three-day shoot, where she was fitted with a prosthetic head, contact lenses and dentures.

Wearing a body suit, she then took her place within the complex set, having to contort her body into a kneeling position and arch her back for the entire 11 hours of shooting, before spending a further hour at the end of the day having everything removed.
The Runaway Bride Gallery has been updated with photos of Empress of the Racnoss, and can be viewed by clicking HERE.