Just came across an article in the New Zealand Womens' Weekly in which James Hewitt is interviewed about the likihood of him being Harry's father. The key dates are:
29 July, 1981: Charles and Diana marry
21 June, 1982: Prince William born
15 September, 1984: Prince Harry born
September 1986: Diana and James Hewitt begin affair
1991: Affair ends whicle James is away with the army
9 December, 1992: Formail separation of Charles and Diana
So, if we're to believe James Hewitt, he couldn't be Harry's dad.
As an interesting aside, Hewitt also claims that he was treated unfairly by the army:
"He was drummed out of the army for adultery and has stuggled since to establish himself in any sort of career. Hewitt remains bitter that the same treatment wasn't meted out to Prince Charles - also an army officer and also an adulterer.
"Let's face it, he was the one who was sleeping with an officer's wife (Camilla) for years," says Hewitt. "He is still an officer in all three forces. In fact, he has been promoted. I'm not complaining. I transgressed the army's rules and I was dealt with accordingly. All I'm asking for is for the rules to be applied evenly and for attitudes to reflect that."
Lady Grace