‘Good morning,’ he said. ‘My name is Robert Cornwallis. I understand you wish to discuss a funeral plan with us.’

‘Yes.’

‘You’ve been offered coffee or tea? Please come this way.’

The new client was taken down the corridor to a room at the end. This was as understated as the reception area – with one difference. Instead of books there were folders and brochures which, if opened, would show images of coffins, hearses (traditional or horse-drawn) and price lists. A number of urns had been arranged on two shelves should the discussion veer towards cremation. Two armchairs faced each other, one beside a small desk. Cornwallis sat here. He took out a pen, a silver Mont Blanc, and rested it on a notepad.

‘The funeral is your own,’ he began.

‘Yes.’ Suddenly Mrs Cowper was brisk, wanting to get straight to the point. ‘I have already given some consideration to the details. I take it you have no problem with that.’

‘On the contrary. Individual requirements are important to us. These days, pre-planned funerals and what you might call bespoke or themed funerals are very much the mainstay of our business. It is our privilege to provide exactly what our clients demand. After our discussion here, and assuming our terms are acceptable to you, we will provide you with a full invoice and breakdown of what has been agreed. Your relatives and friends will have nothing to do except, of course, to attend. And from our experience I can assure you that it will give them great comfort to know that everything has been done exactly in accordance with your wishes.’

Mrs Cowper nodded. ‘Excellent. Well, let’s get down to it, shall we?’ She took a breath, then dived straight in. ‘I want to be buried in a cardboard coffin.’

Cornwallis was about to make his first note. He paused, the nib hovering over the page. ‘If you are considering an eco-funeral, might I suggest recycled wood or even twisted willow branches rather than cardboard? There are occasions when cardboard can be … not entirely effective.’ He chose his words carefully, allowing all sorts of possibilities to hang in the air. ‘Willow is hardly more expensive and a great deal more attractive.’

‘All right. I want to be buried in Brompton Cemetery, next to my husband.’

‘You lost him recently?’

‘Twelve years ago. We already have the plot, so there’ll be no problems there. And this is what I want in the service …’ She opened her handbag and took out a sheet of paper, which she laid on the desk.

The funeral director glanced down. ‘I see that you have already put a great deal of thought into the matter,’ he said. ‘And this is a very well-considered service, if I may say so. Partly religious, partly humanist.’

‘Well, there’s a psalm – and there’s the Beatles. A poem, a bit of classical music and a couple of addresses. I don’t want the thing going on too long.’

‘We can work out the timings exactly …’

Diana Cowper had planned her funeral and she was going to need it. She was murdered about six hours later that same day.

At the time of her death, I had never heard of her and I knew almost nothing about how she was killed. I may have noticed the headline in the newspapers – ACTOR’S MOTHER MURDERED – but the photographs and the bulk of the story were all focused on the more famous son, who had just been cast as the lead in a new American television series. The conversation that I have described is only a rough approximation because, of course, I wasn’t there. But I did visit Cornwallis and Sons and spoke at length to both Robert Cornwallis and his assistant (she was also his cousin), Irene Laws. If you were to walk down the Fulham Road you would have no trouble identifying the funeral parlour. The rooms are exactly as I describe them. Most of the other details are taken from witness statements and police reports.

We know when Mrs Cowper entered the funeral parlour because her movements were recorded on CCTV both in the street and on the bus that took her from her home that morning. It was one of her eccentricities that she always used public transport. She could easily have afforded a chauffeur.

She left the funeral parlour at a quarter to twelve, walked up to South Kensington tube station and took the Piccadilly line to Green Park. She had an early lunch with a friend at the Café Murano, an expensive restaurant on St James’s Street, near Fortnum & Mason. From there, she took a taxi to the Globe Theatre on the South Bank. She wasn’t seeing a play. She was on the board and there was a meeting on the first floor of the building that lasted from two o’clock until a little before five. She got home at five past six. It had just begun to rain but she had an umbrella with her and left it in a faux-Victorian stand beside the front door.

Thirty minutes later, somebody strangled her.

She lived in a smart, terraced house in Britannia Road just beyond the area of Chelsea that is known – appropriately, in her case – as World’s End. There were no CCTV cameras in the street, so there was no way of knowing who went in or left around the time of the murder. The neighbouring houses were empty. One was owned by a consortium based in Dubai and was usually rented out, though not at this particular time. The other belonged to a retired lawyer and his wife but they were away in the South of France. So nobody heard anything.

She was not found for two days. Andrea Kluvánek, the Slovakian cleaner who worked for her twice a week, made the discovery when she came in on Wednesday morning. Diana Cowper was lying face down on the living-room floor. A length of red cord, normally used to tie back the curtains, was around her throat. The forensic report, written in the matter-of-fact, almost disinterested manner of all such documents, described in detail the blunt-force injuries of the neck, the fractured hyoid bone and conjunctiva of the eyes. Andrea saw something a great deal worse. She had been working at the house for two years and had come to like her employer, who had always treated her kindly, often stopping to have a coffee with her. On the Wednesday, as she opened the door, she was confronted with a dead body and one that had been lying there for some time. The face, what she could see of it, had gone mauve. The eyes were empty and staring, the tongue hanging out grotesquely, twice its normal length. One arm was outstretched, a finger with a diamond ring pointing at her as if in accusation. The central heating had been on. The body was already beginning to smell.