The sub on the rocks off Skye and the Russian sub being off the Nato radar, which I wrote about this morning, have something in common - Nimrod aircraft.
The presence of at least one USAF Orion P3 subhunter at Kinloss is being linked to the search for a Russian Akula class nuclear submarine somewhere in the Atlantic. This is exactly the situation that critics argued would happen if the RAF Nimrods flying out of Kinloss were scrapped.
Simultaneously a Royal Navy submarine has run aground off Skye - Ross MacKerlich of Kyle was giving a fantastic eyewitness account to Radio 4 just now - stranding a nuclear reactor and 7800 tonnes of expensive, and secret, equipment on a rock. You can be sure that it won't just be tourists up there taking pictures this afternoon and consequently that every numberplate crossing the Skye bridge today will be cross-checked by the police and the security services.
But who guards these guardians? When a nuclear sub is approaching home base, or gets into trouble in home waters, a Nimrod aircraft usually provides a protective curtain by dropping sonar buoys in the sea along its course and listening for any approaching enemy submarines.
Without Nimrods they'll need helicopters or frigates to do the job, and if there is a Russian sub on the loose somewhere, unaccounted for, the task becomes even more urgent.
A Royal Navy spokesman has explained that the submarine was maneuvering at low speed, alongside a small when she grounded. The Royal Navy are awaiting a highly technical solution to the problem - high water at 7pm - so the sub can float off.