Apologies in advance for my Demon network history pedantry 😜
158.152.1/24 was reserved for Demon service and network infrastructure hosts. Customer accounts were allocated static IP addresses later in the block, with founding members starting from 158.152.8/24. Back then there was a certain kudos attached to having a low numbered Demon IP address as it showed how much of an early adopter you were!
Giles’ dialup account was rundart.demon.co.uk, I think gt.demon.co.uk was his office machine (hence being in the ‘internal’ network range).