Hacking attempt.

[Duke Speedy of Leighton]

Black coooouuunnntray is nearest toooze pure Anglooooo-Saxon as yas gets. 

[Techno]

An easy example: the Strine accent is clearly Cockney, but with no glottal stop, so we can be pretty sure Lunnun English picked that one up fairly recently.

I was thinking about where the Australian accent had come from, just a few days ago !....I'd never noticed that it had Cockney 'roots'.
Nice one, Alexander

[d_Guy]

I always wondered how they know that.

I've watched a bunch of YouTube vids on the subject. One common way is to note that certain words are intended to rhyme, as in Shakespeare for instance, and they no longer do in received English. They often will rhyme when using  my hillbilly twang.

[Leon]

What do you island folk call a tar arn?

That would be a crowbar or a lug wrench!  Crowbar if it's just the 'J' shaped bit of metal for popping tyres on/off, lug wrench if it's an 'X' shape and got sockets on it.