XJR6 Serious Oil Loss

Long story short. 1997 XJR6 55000 miles only.
Did 250 mile journey parked overnight started car Oil Light on and Gauge showed Zero, nothing on Dip stick. Refilled drove home 250 miles, checked oil just on botom of Dip Stick. No Oil loss on ground when parked up
Refilled and 2 weeks later took 60 mile drive no problem shown (did not check level) car parked up for 3 weeks. Today went for MOT problem within 1 mile from home no Oil pressure and off Dip Stick!
On ramp at MOT had good look loads of Oil all along bottom of car and seems to be from Autobox to Engine - Crank seal problem? Heeeeelp Please

Obviously a good place to start looking??

Rear crankshaft seal? Ouch!