MD1, known as Churchill’s Toy Shop by bureaucrats who couldn’t control it, was disbanded in 1946.

Since then the Firs has been used as research laboratories for an iron and steel manufacturer, and offices. It is now being converted into flats.

Light Show

This strange looking building is tucked away in the corner of a field near Grendon Underwood. It’s a generator house, used for powering lights arranged in farmer's fields to produce the illusion of runways at night, on a decoy airfield.

The land here is quite flat, which must have helped to make the decoy convincing.

When built the generator house would have been covered with an earth bank, as protection against bombs. The short square tower at this end has manhole steps built into the wall, so it can be used to escape if the entrance door at the far end is blocked. I’d guess there had once been a manhole on the top.

This is the wall with the angled edge you can see in the previous photo. It would retain the edge of the earth bank that covered the building on three sides.

In this retaining wall is the entrance door, not visible here and hard to see anyway, mostly hidden behind tall nettles and discarded branches.

In the middle of the photo is a hole that was probably for the generator’s exhaust pipe. I’d guess that a tube the diameter of this hole ran horizontally out through the bank, and the exhaust ran through this.

Go Round the Back

This was the tradesman’s entrance for the house at Bletchley Park. In WW2 it was the dispatch rider’s gate. Enemy messages were brought here to be decoded from intercept sites all over the country, by motorcycle.

The lane to this gate still exists, running between the rectory and the edge of the Bletchley Park estate.

The BSA WM20 was the most common motorcycle used for dispatch work during World War Two and many thousands were built. There are quite a few left and there’s even a BSA WM20 website for riders of these ancient 500cc singles.

But the bike in the picture isn’t one of them. It’s perhaps just 40 years old, just half as old as some of the surviving dispatch bikes.

A sentry post is tucked away just inside the gate. It’s been rebuilt since I last came here in 2014, when I found the brickwork crumbling.

There seems to be no form of heating, but at least the sentries would be out of the wind and sheltered from rain and snow.

It was a different story for the dispatch rider, who would be out in all weathers.