I've visited all the other Wirral WW2 bombing decoys, except for Hilbre. The decoys were to give the Luftwaffe the illusion that the Dee Estuary, was indeed the Mersey Estuary, so that they would waste their bombs on the mudflats, rather than the port, which was where most of the convoy supplies landed from the USA.
The Luftwaffe usually bombed Liverpool from the south, following the mid-Wales railway line, to the Dee Estuary, and then turned right to be over Liverpool.
Hilbre was the most northerly decoy, the others on the Dee Estuary were Inner Burton Marsh (includes RAF Sealand airfield decoy), Burton Marsh for Garston Docks, Gayton for Lime Street, Heswall, Hoylake, Moreton, Brimstage and Wallasey.
Hilbre is one of three tiny rocky islands, which are easily walkable (at low tide) from West Kirby. They are one of the few rocks on the coast between Blackpool and Colwyn Bay. They are known to have been three islands as far back as Elizabethan times, from the south, they are named "Little Eye", "Middle Eye", and "Hilbre". "Hilbre" is the biggest.
Middle Eye and Hilbre from West Kirby:
There is an organisation, associated with Hilbre and it's conservation: Friends of Hilbre Island
The website describes the islands better than whatever I can.
Between times, they have been a lifeboat station, a buoyage station, and part of the Telegraph system between Holyhead and Liverpool, to inform the pilots as to which ships were arriving for Liverpool.
During WW2, they were also used for the military, and had two decoys, with one control bunker, a "fire" decoy, known as a "QF", and a "lighting decoy", known as a "QL".
The "QF" Decoy was between "Middle Eye" and "Hilbre", the "QL" was west of Hilbre, and consisted of electric lights on poles on the tidal sands. The "QF" imitated burning buildings, and was said to look like "huts on stilts" from the mainland.
This decoy was particulary effective, being mentioned in Luftwaffe reports as on one particular night (29th / 30th November 1940) "Major fires had been faked by the pouring of oil onto the Dee Estuary west of Birkenhead, with the majority of crews mistaking these for fires in Liverpool".
Location, courtesy of MS Live Local - the 3 tiny islands in the centre:
This shows the location of the decoy sites, and the control bunker (courtesy of Google Earth). The "QF" site is between Hilbre (left), and Middle Eye (right):
This shows the first rocks of Hilbre, which is always (must be !) approached from the south, notice the square concrete block, on the right:
The concrete block was to secure the electric cables from the control bunker, over the top of the rocks, down, and then to the "QF" decoy between "Middle Eye" and "Hilbre". The cables were to start the ignition:
The site of the "QF" Decoy, from "Middle Eye":
First sight of the control bunker:
A pre-war aerial photograph of Hibre, showing that there was no bunker previously:
The bunker entrance - the blast wall has disappeared (like all others on other control bunkers !). The escape hatch is on the top, also used as a look-out. The bunker is exactly the same as the one for Burton Marsh.
The diesel generator exhaust vent:
The electrical control cable exit, via a steel pipe:
The electrical control cable routing:
"QF" straight ahead, "QL" to the right:
Despite being a buried bunker, it still had gutters and drainpipes (!!!), exactly the same as the example at Moreton nearby:
To conclude, the Telegraph Station:
The Telescope mounts for spotting ships (in comfort !) - now superceeded by AIS Liverpool: Ship AIS
Courtesy of a "Friends of Hilbre" member, an original "QF" site firebar, from the Moreton decoy, a few miles away: