IT is understandable that many people baulk at the idea of spending £20 billion to replace our Trident nuclear deterrent, but that figure should be put in persective.

Firstly, as the cost will be spread over three decades, it comes to less than £1 billion a year. Compare that to our GDP last year, which was about £1,240 billion.

Alternatively, compare the total cost to the annual cost of our EU membership. Several studies have come up with estimates in the region of £50 billion a year net costs for belonging to an ill-conceived international organisation which is doing incalculable harm to our country. How much better to spend £20 billion to defend it, equivalent to just five months' worth of those EU costs.

Indeed, there is a strong rumour that when the Treasury did its sums on EU membership, its central estimate of the net costs was not £50 billion a year, but £150 billion, which divided by 60 million averages out as £2,500 for each of us every year.

DR D R COOPER, Maidenhead, Berkshire.