L versus LL in British versus US English [duplicate]

Possible Duplicate:
When is “L” doubled?

Is there any guidance on the usage of doubled consonants, particularly L, in British versus US English? For example 'Travelled' v. 'Traveled', 'Cancelled' v. 'Canceled', but then 'Enrolment' v. 'Enrollment'. Then there's 'Travelling' v. 'Traveling' etc.

In each case I've put what I consider to be the British standard first.

Just wondering if there's any consistency, for example 'in present and past participles ending in L the British usage is to add a second L'?

The American rule is to double the 'l' if the last syllable is accented when you add the suffix -ing or -ed, but not if the first syllable is accented. The British rule is to always double the 'l'. This explains most of the differences: traveled, canceled, fueled and so on. (Both sides of the pond double the 'l' in words like propelled where the stress is on the second syllable.)

The word enroll/enrol (note that the spelling difference appears in the base word as well as in the derived enrollment/enrolment) is not part of this pattern, but just an isolated spelling difference that confuses the issue.

One good way to resolve this issue is to use Google ngrams. It isn't perfect but it can give you a good approximation.

Example: Cancelled vs canceled (British)

Cancelled vs canceled (American)