From Piltdown Man to Tokeley Parry’s Egyptian artefacts, the art and antiquities world is always susceptible to fakes and forgeries.

Those produced by the Greenhalgh family varied in quality from the very good to the plain bad. But the most astonishing aspect of this case is the sheer range of material they generated. Not limiting themselves to one period, they dabbled in modern and ancient sculpture, Roman silverware, pastels and watercolours.

This diversity made the task of connecting the dots on this case so difficult. The family also devoted considerable time to falsifying provenance for the objects, making a case for the presence of this material in England for many years.

Many will ask whether scientific techniques could not be used to establish forgeries. But these techniques, while providing extensive supporting evidence, often cannot provide definitive answers.

For the majority of prints and drawings, attribution can be determined only by expert opinion. In the case of antiquities, testing can suggest only likely dates.

When George Greenhalgh Snr brought an Assyrian relief to be examined by the British Museum in 2005, curators in the Middle East Department were alerted to inconsistencies in style and colour.

The most telling signs were an incorrect horse harness and an error in the cuneiform inscription. Cuneiform is the world’s oldest writing and can be read by only a few select scholars across the world. These anomalies were suspicious enough for them to alert the Art and Antiques Unit of the Metropolitan Police, which was able to build a successful case against the family from there.

Expert vigilance is the best defence but the battle seems, and probably is, never-ending.

— Andrew Burnett is deputy director of the British Museum

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