On Mon, 27 Dec 2004 17:32:51 +0000, Mrs Redboots
wrote:

Michael Bell wrote to uk.transport.london on Mon, 27 Dec 2004:

I think rhythm is important here, many people break phone Nos into triplets,
but it's into duplets on the continent.

Really, of course, we should quote London numbers in the same way that
we quote every other number (mobiles included) - as a group of 5
followed by a group of 6. But it's horrendously difficult - I can't do
it in my head with my own phone number, never mind anybody else's!

Why a group of 5? The area code is only 3 digits long.