Your father could buy what is referred to as a purchased life annuity, this is an annuity bougth from a life company that only a element is taxed as income and the remainder is seen as a repayment of capital.
However annuities are generally not considered very good value for money and typically die with the annuity purchaser unless provision is amde when buying the annuity for a spouse or financial dependant, such a provision costs and reduces the annuity payable.
Depending on the level of money in question, independent financial may be worth considering.