In looking through MK Electric’s online catalogue I came across the remark that certain outlets are “… fitted with two earth terminals to provide a double earth facility for use when installations are to comply with Regulation 607 of BS.7671, IEE Wiring Regulations”.

In what kind of situation is this regulation applied and how is the earthing system wired?

As far as i am aware its for outlets that supply computers,

Some else might throw more light on it, but in large office situations you run a parallel earth to the outlets supplying the PCs.

This is i think because the PCs have a large earth leakage..

Yes, the double earthing is commonly specified for circuits feeding multiple computer systems.

No apologies for providing yet another link to the very useful TLC-Direct on-line brief guide:
http://www.tlc-direct.co.uk/Book/7.8.2.htm

Paul,
Some information on your link is now a little dated. Electricity Supply Regs have now been replaced with Electricity Safety Quality and Continuity Regs.
Also, caveat of 25% is no longer a requirement of bs 7671 2001 although it is a useful guide.