You are saying the opposite!

She was only carrying her B Permit. She Didnt have a Transit Visa.

:-)...Man..trust me.. I searched all websites the UK Government( UKBA and Foreign office) had to offer .

my wife went to India Via Heathrow without a Transit Visa.
We got it verified with BA Counter at Geneva.
maybe the following link will help you.

http://www.ukba.homeoffice.gov.uk/si...quirements.pdf

Check

a valid common format residence permit issued by an EEA State or Switzerland pursuant to Council Regulation (EC) No. 1030/2002.

The current card permits issued by Switzerland are pursuant to Council Regulation (EC) No. 1030/2002.

We carried this PDF when we went to th Airport and showed it to the BA desk. Offcourse, they were already aware of thisl

Hope this finally clears the confusion.

I have found the following document which explains the transit without a visa (TWOV) option in UK. Apparently, with a valid residence permit from Switzerland TWOV is possible. You can access the document from here:
http://www.ukba.homeoffice.gov.uk/si...quirements.pdf

Didn't I say the same may years back in the same thread ;-)
This is valid since Switzerland started issuing new format B permit

I am from the countries listed third world with permit C. I just came back from a trip transiting Heathrow Airport with a friend who has permit B. I know this is a old thread but want to encourage others with these permits that they can transist London without any transist visa. After reading the comments here, we had had to go to the airport and confirm what is been said here ourselves. To our surprise we could travel with British airline and we just got back last week! British airline is very cheap to travel with compare to others.