"Jim" wrote in message
...

the idea that the Oyster will be "clever"

That's the plan. Whether the software programmers have been clever enough
remains to be seen!

if I beep my new Oyster in at Highbury, there is no
NLL to beep in out of, beep it in at West Hampstead Jubilee and out
at Harrow Met, how will it know I have used the North London Line?

Does Finchley Road and Frognal not have Oyster pads?

Will it assume I have gone via Kings Cross and charge me an extension
ticket. Alternatively, if I am going via central London (if I miss a
NLL or it's late) and I go via Kings Cross will I get charged twice as
I go through 2 sets of barriers - Higbury to Kings Cross and Kings
Cross to Harrow?

Places like Kings Cross already recognise "out of station interchange" for
magnetic tickets, so it *should* be the same.

It's going to be a case of try it and see what happens I'm afraid. You can
check what journeys you have been charged for yourself using one of the
large self service ticket machines.