How do I re-ignite the pilot light on an old Kingfisher boiler?

This is an old model Potterton Kingfisher CF180 Cat 1N (whatever that means). There are two buttons - one white with a flame motif above a red one with a dot. There is also a dial to the left showing a temperature range from 30 -90 (It has been on 60 for years)..Pressing in the white button seems to release the gas - I can light it with a match - I hold the white button in a few seconds - let go - it then releases slowly - but the pilot goes out! and no whoosh where the whole thing starts working . What is the red button for ?