It says for the policy to remain valid, the vehicle needs current MOT & VED...
I don't think you can SORN a car with a tax disc. It's one or the other, if you SORN it then you have to send the disc back. It's a real PITA.
When they changed the law to make all taxed cars have insurance even if it was on blocks without an engine they made life difficult for the honest bloke again. All because they cannot be bothered to catch the criminals who drive without insurance, so they penalise everybody.
This is another case of pre-judging people, guilty before being proven so, they assume the car will be used on a public road even though you have declared it SORN.
They have made it very difficult for the owner of the off the road vehicle, to sell it, without road tax, even though the MOT may still be current.
They should re-introduce insurance where the person is the one being insured, not the vehicle, after all it is the individual who builds the reputation for being a safe driver over a period of years.
A car is just an innamate object it does not have accidents on it's own.
Wotan