The first clue that an Indian-owned tanker was involved in secret trades came from tracking data that showed it had mysteriously jumped 4 km from its last known position.

The clincher was the satellite images that suggested that the 300,000-dwt Giessel (built 2002) had shrunk from 333 metres in length to 275 metres.

Researchers at Israeli company Windward concluded that the Giessel was an early exponent of the “AIS handshake” — passing its own digital footprint to a nearby decoy vessel, while simultaneously going ‘dark’ by switching off its AIS.