Time to change the oil. Last change was a year ago.
First dump the old oil.
Remove the filter and refill the new filter with fresh oil. Oil the seal too and clean the seal contact surface from the engine.
Comparison shows how much longer the new filter is. This gives more filter material. But makes the ground clearance a little bit smaller.
I have always used mobil 4t racing. It had worked ok and it is what triumph recommends.
I usually check the old filter by pressing.the flow back valve and draining the dirt from the filter. It usually has some metal flakes, but triumph has been very good and doesnt get flakes like many of my previous bikes had.
Now it needs just driving.
Oil pressure returned almost immediately as filter was prefilled.