Shannon vs Shanwick

[None]

What is the protocol to receive a new oceanic entry clearance when too early at the entry point?

We were airborne EINN and going to be 10 minutes early at the entry point, so we told Shannon Center. They said they would send the revised estimate to Shanwick. About 10 minutes later we asked Shannon if we were cleared to enter the track at the revised estimate, their response being "we have revised the estimate with Shanwick." So, are we cleared in, or have they only revised the estimate? After a few more radio calls we cleared it up. What were we suppose to have done? (Should we have called clearance delivery in the air? Does that go right to the authority?)

[Numpo-Nigit]

It's a while since London ACC had a direct interface with the Shanwick boundary, so my recollection may be out-of-date. However, assuming you were flying a jet, my understanding is that it is your responsibilty to recall the Clearance Delivery frequency for a re-clearance if you are unable to comply with the clearance that has been issued. Different rules may apply to propeller-driven aircraft.

[Jumbo Jockey]

If in doubt the answer must always be to query direct with Shanwick to make sure. This is in compliance with a rule of thumb I have always found useful under such circumstances: I'd rather do something it subsequently turns out I didn't have to do (in this case re-check with Shanwick) than NOT do something I should have!