‘Garcia had his model on a small wheeled platform,’ said Alleyn. ‘Now, Malmsley told us that Garcia proposed to wheel the model into the case and then put the whole thing on board whatever vehicle called to collect it. I think he changed his mind. I think he put the empty crate in the vehicle, drew the stool up to the sill, and wheeled the model over the sill into the crate, and aboard the caravan which was backed up to the window in the lane outside.’

‘The caravan, sir?’ asked Sligo. ‘Was it a caravan?’

‘Lock this place up and come along outside. You can get over the sill, but don’t touch those two marks just yet. Jump well out to the side and away from the tyre-tracks.’

In the lane Alleyn showed them the traces left by the wheels. They had been frozen hard.

‘Bailey has taken casts of these, but I want you to note them carefully. You see at once that the driver of the van or whatever it was did a good deal of skirmishing about. If there were any footprints within twelve feet of the window, they’ve been obliterated. Farther out are traces of the mortuary van, blast it. The caravan tracks overlap, and there are four sets of them. But if you look carefully, you can pick out the last impression on top of all the others. That’s when the van was finally driven away. The next set, overlaid by these, represents the final effort to get in close to the window. Damn! It’s beginning to rain. This will be our last chance in the lane, so let’s make the most of it. Observe the tread, Sligo. There, you see, is the clear impression of a patch. I’ll measure the distance between the wheels and the width of the tyres. There a little oil has dripped on the road. The van or whatever it is has been recently greased. It was backed in and the brakes jammed on suddenly, but not quite suddenly enough. The outer edge of the window-sill has had a knock. The front wheels were turned after the vehicle had stopped. There are the marks. From them we get the approximate length of the wheel-base. Out in the middle lane they disappear under the tracks of more recent traffic. Now look at the branches of that elm. They reach across the lane almost to our side, and are very low. I wonder the county councillors have not lopped them down. Do you see that one or two twigs have been snapped off? There’s been no wind, and the breaks are quite recent. See here!’

He stopped and picked up a broken twig.