When Pope answers the 'phone, he says "Bermondsey 01-237". Bermondsey is an area of London. The telephone numbers 01 represent London, and 237 represents Bermondsey (cf 'B-E-R' on a modern alphanumeric keypad). The actual unique telephone number is the four digits that would have followed those two codes, such as 01-237-2345. What he says is the UK equivalent of a US person saying "This is 1-800" or "... 555".