Nasty loose ends on company closure

Young company, always loss-making, is wound up. Formed by A as sole director and shareholder, but funded as a loan by a company owned by A's friend, B.
Upon winding up B wrote to A writing-off the full value of the debt.
After settling with all other creditors there was some money left in the bank and on closure of the account A paid it to himself.
Some time elapsed before B got wind that there had been some cash left and began to make things a little uncomfortable for A.
A decided that for a quiet life he would make a payment to B.
The question: Is it right to take the payment to B into account when calculating A's personal tax liability, bearing in mind that he seems to be under no contractual obligation to have made it?
Thanks in advance for your comments.