I know Marnham and admire his writing but I was forced to point out (as Walter Winchell used to say) that his central theory collapsed from a monumental mistake of geography – he had Lucan and his hired killer moving between Lower Belgrave Street and the Lucan mews house behind. I reviewed Trail of Havoc for this paper ( LRB, 12 November 1987). Hill cites Marnham’s book Trail of Havoc as a source for the intruder theory. Veronica was talking about her husband trying to kill her. ‘When they are old enough to understand,’ he wrote to Bill Shand Kydd, ‘explain to them the dream of paranoia, and look after them.’ Hill opens her piece with Veronica’s question to Dominick Elwes from behind her bandages in her hospital bed: ‘Now who’s the one with paranoia?’ Hill doesn’t follow this up. Like Aitken’s sword of truth speech, Lucan’s letters have a giveaway mixture of fake nobility and self-pity. However I won’t bore you with anything.’ They are Etonian letters par excellence – the first skill you acquired in that brutal age at Eton was lying, vide Jonathan Aitken.

To Michael Stoop he wrote: ‘I have had a traumatic night of unbelievable coincidence. Why believe them instead of all the massive evidence against him? Lucan’s only description of the intruder is of a ‘large man’. Where does the intruder story come from? Only from Lord Lucan’s letters written that night, trying to set up a version to save his children’s shame, before he committed suicide. ‘That he was desperate enough and able … to hire a hitman seems more plausible,’ Hill writes, ‘that he panicked at the reality and tried to stop the killing, arriving when Rivett was already dead and his wife wounded.’ More plausible, she says, because Laura Thompson and two other writers, including Patrick Marnham, all think that ‘whatever his state of mind, he (Lucan) was not capable of such extreme, sustained violence.’ How do they know? What is that based on? Shouldn’t Hill have been more sceptical of this? But it’s fascinating in terms of historical myth.

That Rosemary Hill buys it too is odd but more excusable – she’s getting it from the book or books. It is bizarre after all this time to find any writer on the case, who is not a family defender of the disappeared earl, putting across such a conclusion. From Rosemary Hill’s review, it seems we have another book, this by Laura Thompson, exonerating Lord Lucan of the murder of the children’s nanny, Sandra Rivett, and the attempted murder of his wife, Veronica ( LRB, 5 February).

Lord of the deep by dawn thompson