If Altona Gate is the one I think it is, we got to it by driving along Blackshaws Rd and down Millers Rd. It was 'discovered' by Andrew Bowman and was originally known as Bowman's Flying Circus as it was anticipated that considerable air time would be logged. Mike Stone's young kid couldn't say Bowman and it came out as Bumbo, of course that name stuck and it became known as Bumbo's Flying Circus. A young Ian Ross aka Black Ian and later Foxy, got a can of paint and a paint brush and put a number on anything that looked remotely climbable. Some of these took a while before they were climbed and of course people found climbs between the climbs and these were labeled with a number and a suffix (eg "a"). It all happened back in the early '70s, probably.
Now excuse me while I go looking for my memory pills, I know I put them down somewhere safe.