When walking along the Victoria Lines, in the stretch between Naxxar Gap and Wied Anġlu, one can see on the low ground beneath, a peculiar, concave, concrete structure, surrounded by telecommunications antennas. Although the antennas are modern, the structure itself dates back to the 1930s, and was a precursor to radar, intended to protect Malta from air attack.
Throughout the 1930s, mounting tensions between Great Britain and Italy, and fears that the Italians might launch a surprise invasion of Malta, led to a reassessment of the island’s defences. Pillboxes were constructed to defend key points, while barbed wire entanglements and other obstacles ringed Malta’s coastline. The old coastal forts came alive again, as a programme of rearmament was launched.
Yet, whereas up to this point, the main threat to the Maltese Islands had always come from the sea, the fact that Sicily was only thirty minutes flying time away meant that the aerial threat was now much more serious, and new measures had to be taken. One of these was the construction of an experimental early-warning system, known as a Parabolic Acoustic Mirror, or “il-Widna” (the ear), as the locals aptly called it.
The concept of acoustic mirrors was developed in the interwar period. These concrete structures were intended to detect incoming enemy aircraft by listening for the sound of their engines. Over a dozen such structures were built along the south coast of England, the most famous of which still stand at Denge, on the Dungeness peninsula, and at Hythe in Kent.
Further acoustic mirrors were planned for the British outposts of Malta, Gibraltar, and Singapore, although in the end, only in Malta were a number of suitable sites identified. The first to be built was the one at Magħtab, on Malta’s northern coast. The acoustic mirror would face the direction of Sicily, with an area of flat land directly in front of it, and then the open sea. Construction began in late 1934, and was completed by the following summer, at a cost of around £4,500. The electrical equipment was installed in early September 1935, with testing and training of the operating staff beginning soon after.
The curved concrete wall measures 61 metres wide by 7.6 metres high. In front of it is a sloping expanse of concrete and a trench, where twenty very sensitive microphones would have been located. Their output was interpreted by operators in a small room at the back of the mirror. The structure was painted in a special camouflage scheme to help it blend into the surrounding landscape, particularly when viewed from the air.
Trials showed that it was effective at a range of over 25 miles, although operators needed to be highly trained before these levels of sensitivity could be achieved. In contrast, the range of the unaided human ear was put at five miles. It was estimated that the mirror would provide a six-minute warning of an enemy aircraft approaching Malta at 250 mph. Yet the increasing speed of aircraft in the 1930s suggested that in the near future, that time window would be significantly reduced. Additionally, the development of radar as the decade progressed finally put an end to further experimentation with acoustic mirrors for air defence.
Then known as RDF (Radio Direction Finding), radar was first introduced to Malta in March 1939, with the establishment of Air Ministry Experimental Station (AMES) Nº 242 on Dingli Cliffs. This was the first of its kind to be installed anywhere outside the United Kingdom, and the number of such stations would be increased to eight by late 1943. Radar would play a huge role in the defence of Malta during World War Two, not only aiding Allied pilots to intercept Axis air raids, but also enabling civilians to seek refuge underground before the arrival of enemy bombers.
Today, “il-Widna” serves as an earth station for a local telecommunications company, hence the modern antennas. Because of the change of plans in the 1930s, the other acoustic mirrors that had been planned for Malta were never built, and thus the one at Magħtab was the only one of its kind built on the island, and the only one to have been constructed outside of the British Isles.
This article first appeared on the Air Malta in-flight magazine, Il-Bizzilla