I have a strange knock coming from the brake master cylinder / offside chassis rail / steering column / front strut area (UK right hand drive car). I've been going through the suspension arms and have replaced the rear lower (front) arm as well as the drop links. The front lower arms seem fine at the moment. I am happy that there is no excessive play in the engine mounts as there is no excessive movement when revving and no clonk in the drivetrain usually associated with a worn mount.
The knock sounds as if a heavy electrical plug (or similar plumb weight) is swinging and knocking on the chassis somewhere. The knock is consistent with bumps but does not increase or decrease with braking/acceleration or cornering.
With the car up in the air (so obviously stationary and engine off) I can make this knock by giving the engine a good sideways shove. When doing this it sounds like the engine itself is knocking one of the a/c pipes or the steering column but I can't see any witness marks - can't really see too much of anything in this area with the FBH gubbins! I've had both skid plates off to look, the bulkhead trims off to look, underside of the dash, offside wheel arch liner......
FBH and its exhaust are all tight. Engine exhaust is all tight and not in contact with anything.
Any ideas fully appreciated as it's driving my nuts!

Hydraulic engine mountings knock when they run out of oil. Its a common Jaguar fault, so LJR must use the same parts in common. Try lifting the engine with a pry bar adjacent to the mountings. I have seen it on Youtube recently too. Try Baz Meredith's channel.

Hi Jagracer.
Thank you for this. Lifting the engine will allow the mount to refill with oil?

No, when they fail the oil drains out. They act as a shock absorber, and break apart internally. Oil underneath is a good clue. Without the oil, the engine will flop about and knock.