Britdopers - "Jesus Wept."

Brit here,JW is a lot less commonlly used nowadays.

It is pretty much a situation specific expletive IMO being used when angry as a condemnation of stupid behaviour when a higher level of common sense would be generally expected.

An example would be on discovering that a delivery of paint stripper has been left beside an open fire.

If really,really angry "Fucking is often interspersed between J and W.

That’s the context in which I’m most familiar with it - an exclamation bemoaning some calamity, frustration, accident or misfortune.

Jezum Crow on a crutch