I started up my Jaguar the other day after not running it for some time.
Currently I'm running Kendall GT-1 10/40W oil with Lucas oil treatment.
At cold idle it really made a racket. Sounded like a diesel!
I drove it for a while and it seemed to quiet down. I made a YouTube video to demonstrate.
Please have a listen and let me know what you think. Cam chain?
I had it replaced 3 years ago! Or is it just cold and waiting for oil to distribute?

 

03.1-09 (jagrepair.com)

Oil treatment to loosen the sliding piston in the chain tensioner ?

Yours looks like the original tensioner above the Camshaft Position Sensor ( hockey Puck with the small window )

I prefer a brand of Rislone oil treatment in the yellow bottle at the local parts store

Put this in before a oil change , run for awhile and drain with a fresh no Rislone oil change

It contains Toluene as the main ingredient

It takes some time to loosen up the tarnish with some run in time

There are some oil viscosity recommendations other then what you are using to aid in the one aspect of concern of start up rattle

The revised tensioner can be identified by the arrow cast in the tensioner and they can be harvested from the salvage yard