From RACottrell's link:
Quote:Get your phone connected. All college rooms have phone connections (part of the NTL system). You will need to provide your own phone. Dial 0800 013 6556 to find out your extension number. To receive calls, caller should dial 0845 045 4884 (note: expensive from mobiles) followed by your extension. To make outgoing calls, you need to get a rechargeable calling card from the lodge.
It's 0845 which is unusual, as most universities seem to have implemented systems which use 0870 numbers. It's interesting to see that they've put that it's expensive to call such numbers from mobiles. It suggests that they are (sort-of) aware that 0845 isn't the same as a local call.
Anyway, back to trying to find the number. As it's not a block of numbers we're looking for (which correspond to individual extensions), but one number, it's rather like trying to find a needle in a haystack. Needless to say, this doesn't put use off searching.
When you ring another number (mobile, landline etc), I presume that it comes up "Withheld number". Try dialing 1470 infront of the outside number as this gives the number out on a line which is set to be perminantly withheld. The 1470 code will come after any prefix to get an outside line, if there is one. For example, if you have to dial 1234 to get an outside line, dial 1234 1470 07789 78912 etc. When you do this, see if the number is shown on the receiver's caller display or 1471. Probably easiest to try by ringing your mobile.
Universities are covered by the Freedom of Information Act, see
this page on Cambridge's site. That's one avenue you could go down.
However, if they've not used 0845 for revenue generating purposes, they may be happy to provide the underlying geographical alternative(s) on request. I understand that these 0845 numbers can't be called from many overseas providers, so maybe that can be given as a reason to release the numbers.