I read once that when they were testing the Vanguard and getting engine failures an inboard was shut down
When a crew member went aft he was surprised that the vibration was much more reduced that he would have expected.
So after a discussion they shut the other inboard was shut down and the vibration was virtually gone.
It then went on the say they realised then the wash was coming off the inboard props at just the right frequency to cayuse the most vibration the drumming all the way along the fuse.
It concluded that to eliminate it they would have to shift the engines and therefore redesigning the wing and undercarriage and make changes to the rear fuse and it was decided the changes were too big to be made and with agreement of both BEA and TCA it was left.
I only read that in on source so can't verify
One thing I have seen mentioned more than once was the vibration moving along the fuse with each strip lamp flickering off momentary in turn on the Invicta Vanguards.
What ever the reality it did get known as the Vickers Vibrator.
I wonder if the Orion version would have been better...on that score
The other aircraft designed to take the Orion but fitted with Tynes, the CL-44, suffered such bad vibration on it's first flight the instruments were at times difficult to read and an engine became loose
