A recent case in which the son of an elderly man challenged an alteration made to his father’s will shortly before he died shows how high the hurdle is set when attempts are made to revoke a will on the ground that the person making it lacked mental capacity.

The man had lived with his partner since 1997, following his divorce in 1989. In 2009, seriously ill with motor neurone disease, he arranged for his solicitors to add a codicil to his will giving his partner an annuity of £12,000 a year from his estate, a car and the right to remain for life in the home they had shared. Some months later, the man died.

The man’s son, who was also his executor, was the sole beneficiary under his will before the codicil was added. He opposed the codicil, arguing that it was void for ‘want of capacity’ (ie. that his father was not of sound mind when it was executed) and for ‘want of knowledge and approval’ – ie. that his father did not fully understand the effect of the codicil.

He alleged that his father was a near alcoholic who had suffered from declining physical and mental capacity in the period before his death.

Both sides produced expert medical evidence in support of their positions but the judge was clear that the codicil, which had been drafted with the advice of an independent and experienced solicitor, was valid.