Im sorry if this has already been discussed, but as I dont have the boxset I cannot confirm it. Does it say "portsmouth" on the side of the black rock. Do us brits have a part in the islands history?

Yes, that's right.here is a pic that will help.

http://lost-media.com/modules.php?name=coppermine&file=displayimage&album=445&pos=40

It does say Portsmouth, which indicates that the Black Rock was registered there.

It would well have been built at Portsmouth. It has a long history, and was especially productive around the turn of the 19th Century, which fits with the Black Rock timeline.