Clouds of Witness by Dorothy L Sayers

" -- and the moral of that is -- " said the Duchess. - Alice's Adventures in Wonderland

A party of four were assembled next morning at a very late breakfast, or very early lunch, in Lord Peter's flat. Its most cheerful member, despite a throbbing shoulder and a splitting headache, was undoubtedly Lord Peter himself, who lay upon the Chesterfield surrounded with cushions and carousing upon tea and toast. Having been brought home in an ambulance, he had instantly fallen into a healing sleep, and had woken at nine o'clock aggressively clear and active in mind. In consequence, Mr. Parker had been dispatched in a hurry, half-fed and burdened with the secret memory of last night's disclosures, to Scotland Yard. Here he had set in motion the proper machinery for catching Lord Peter's assassin. "Only don't you say anything about the attack on me," said his lordship. "Tell 'em he's to be detained in connection with the Riddlesdale case. That's good enough for them. " It was now eleven, and Mr. Parker had returned, gloomy and hungry, and was consuming a belated omelette and a glass of claret.