OF all the bric-a-brac bits of concrete leftover from the Second World War which still litter our countryside and beaches, perhaps the most curious are the remains of the Starfish sites.

Starfish was the name given to Special Fire – or SF sites – which were fake towns laid out on open fields and set fire to in order to attract the Luftwaffe’s eye and draw its bombs.

There were 237 Starfish sites across the country protecting 81 cities, and the remains of at least two in our area are now listed buildings.

One is at Great Burdon, on the eastern edge of Darlington in a field where diggers are currently widening the A66, and the other is at Osmotherley, on the edge of the moors above the dam end of Cod Beck Reservoir.

In both places it is the concrete control bunker that has survived. From it, airmen activated special effects that had been developed in film studios to fool the bomber pilots into thinking they were looking at a town which was burning after the Pathfinders, always the first wave in a bombing raid, had dropped their markers on it.

The Darlington site appears to have been staffed by to 14 men, who were billeted in houses in Haughton, and they used steel tanks, pipes, troughs and grids which made their various fuels - oil, paraffin or creosote - pour, trickle or spray upon a source of ignition at timed intervals. These made it look as if different parts of the town, from industrial complexes to domestic residences, had been hit.

A typical Starfish site had 14 Boiler Fires, in which oil was periodically released from a tank on to a steel tray which was heated by a coal fire so that the oil vaporised. At sporadic intervals, water was dropped on the tray creating huge flashes of white flame that leapt 40ft into the air.

Then there was the Grid Fire which sprinkled paraffin on to a hot metal grid covered with metal shavings. It burned with a steady yellow flame.

Coal Fires also looked pretty from the air. They were 20ft long and packed with creosoted firewood and lump coal. A warming deep red glow could be seen from miles around when they were lit - and for variety, a sprinkler pipe would feed diesel oil on to the coals.

Most Starfish sites were protected by earth firebreaks, to prevent the fires getting too real. The best example of these seems to be on Sneaton Moor, above Whitby, which, with Osmotherley, was one of six designed to protect Middlesbrough – the others were at the Middleton, between Stokesley and Yarm, and Kirkleatham, Guisborough and Newton Bewley.

These were operational by June 1941. Darlington’s Starfish – to protect it from bombers coming in from the east coast - was ready by August 1, 1941. Darlington had a second Starfish, at Eryholme, and Durham had one at Sherburn. Hartlepool’s, at Hart, was the last to be constructed, in 1943.

Nationally, the Starfishes are reckoned to have attracted 730 bombing raids, but there is no evidence that either the Darlington or Osmotherley Starfishes were ever lit. Eryholme, which was tended round the clock by four Canadian airmen billeted in Great Smeaton, did go up once – but only because it was struck by lightning.

Most of the Starfishes were decommissioned in 1943, and farmers quickly took back their land, and returned it to crops. Consequently, very little remains, which makes the bunkers at Great Burdon and Osmotherley so interesting.