Just how did this chunk of SpaceX rocket get to the UK?

While traveling around the northern part of Tresco, an island among the Isles of Scilly, boatman Joseph Thomas happened upon a large item floating in the water; it was covered with sea gulls and barnacles, and he thought it may have been a dead whale. He and others attempted to drag it to shore, later thinking it may have been plane wreckage. The debris was eventually hauled inland, and after some of the barnacles were cleared, a large American flag became visible.

Overall, the find measures in at 32ft. x 13ft., and also reads "Falcon 9", revealing that it is (probably) part of a SpaceX Falcon 9 rocket launched from Cape Canaveral, Florida this past June. In that case, the rocket exploded a short while after take off and landed in the ocean.

In the months since, this piece of the rocket traveled about 4100 miles across the ocean to end up near the coast of Scilly. Now that it is ashore and identified, the local Coastguard has the piece of rocket under guard. A warning has also been issued to shipping in the area.

The local Coastguard posted a brief statement about the debris on its blog yesterday, confirming that it is being kept safe. It isn't clear at this point what will become of the debris. You can see the rocket explode in the video below: