Said by someone to communicate either :
* disbelief, or
* a desire to, swiftly, end the conversation or move onto to a new topic
This new version re-kindles the emphasis and weight that its predecessor had lost through overuse.
Often said with a pause to indicate that the speaker has 'upgraded' the statement mid-sentence.
A Brit first overheard it being said by a camp person in L.A and then propagated it to Essex, UK. Therefore, it MUST be said with a fake, camp, US accent every time.
Bob: Oh that's really interesting...someone really should...