‘Well, I hope you’re going into work today, and not just sitting around reading.’ Alma disapproved of such pointless activities. ‘I’m planning on a spot of hoovering.’ She shifted him to clear away the breakfast things.

‘Just in time, I’d imagine. There was a rumour the BBC was coming around to film an insect documentary inside your hall rug.’

‘Are you insinuating I don’t keep a clean house?’ asked Alma, mortified. ‘All these years I’ve been looking after you, with your spilled chemicals and your disgusting experiments. Who fed rotting pork to carnivorous plants on top of his wardrobe during the heat wave of 1974?’

‘That helped me catch the Kew Gardens Strangler, if you recall.’

‘You boiled my tropical fish in 1968, and filled my bedroom with mustard gas.’

‘In order to track the Deptford Demon, as well you know. I didn’t realise your aunt was sleeping in the house at the time.’

She could have mentioned that the ancient detective also grew plague germs in her baking trays and ruined her best kitchen knives putting stab wounds in sides of beef to determine methods of death. He had also rewired the toaster to see if it could be made to electrocute anyone walking across a wet kitchen floor in bare feet, and had been able to answer in the affirmative after nearly setting fire to a Jehovah’s Witness. ‘You filled my sink with sulphuric acid last Christmas, and if I hadn’t been wearing rubber gloves to do the washing up, I’d have ended up in hospital. Took the finish right off my plug, but did I complain?’

‘You most certainly did, madam, and the fact that you bring it up at the drop of a hat reminds me how long you bear the grudge.’ He rose and collected his battered brown trilby from the table.

‘I wish you wouldn’t leave that thing over the teapot; it’s unsanitary.’

‘Most probably, but it keeps my head warm. When you’ve as little hair as I have, such small comforts are appreciated.’ He smoothed the pale nimbus of his fringe back in place. ‘I might remind you that I am still the breadwinner in this household, attending to police work for six decades with an unbroken record, despite your regular attempts to poison me. I could have taken holidays but was too conscientious.’

‘Too scared of missing out on a good murder, more like.’ Alma sniffed. ‘It’s not natural, all this morbidity, especially at your age.’

‘It’s not morbidity, it’s my job. In my field there’s no substitute for firsthand experience. You knew what to expect when you took me in.’

‘I knew you was on the side of law and order; I didn’t expect you to experiment in my lodgings with meat and germs and explosives.’