For the avoidance of doubt and misunderstanding and to shut you two up!
A Private individual can sell a vehicle to whoever he likes. It does not need to be in ANY particular condition, but the seller must not represent the vehicle IN ANY WAY. He must answer any questions honestly.
It is the responsibility of the Buyer to satisfy himself that the vehicle is of a satisfactory quality and suitable for the purpose for which he wishes to buy it. He is expected to perform Due Diligence and makes such enquiries and ask such questions as he thinks fit.
The Principle is Caveat Emptor i.e. Let the Buyer beware.
It is wise to document matters concerning the transaction and have it signed and dated by both parties.
A Trader is a person whose business it is to buy or sell vehicles. If in doubt, H.M.R.C. will determine whether one is a Trader or not.
It is an offence for anyone who trades, to identify themselves as a Private Individual.
A Private Individual who buys from a Trader has the comfort of THE CONSUMER RIGHTS ACT 2015 which places certain Statutory Obligations upon the Trader. The Trader must act in good faith and not misrepresent the vehicle in any way.
It is wise for all details of any transaction to be documented as above.
In the event of any dispute arising out of a Private Sale or with a Trader, the Courts will determine a resolution, authoritatively, having regard to the facts of the transaction. Hence the advice to document everything.
The Lexus Forum in my opinion is not the best place to resolve disputes.