There was much speculation when the Duke of Edinburgh was taken to hospital last June that his bladder infection may have been brought on by his participation in the Jubilee.
Standing for some hours on the royal barge during the river pageant without, as far as we could see, taking a drink or visiting the toilet could have encouraged the infection to take hold as they do when the bladder is not regularly flushed.
But now that the infection has recurred, as it does commonly in men, doctors will be looking for a possible underlying cause.
Especially because that might be something more serious.
The most common underlying causes are a blockage in the tube leading down from the bladder, a bladder stone and problems in the prostate.
My guess is that is what the investigations referred to in today's Palace statement will focus on.
Let's remember that Prince Philip is 91 and any illness in someone so senior is likely to be more serious.
But let's also remember that he's a very active 91 and has enjoyed almost untroubled good health throughout his long life.