Up to 30 police, as well as the police dog squad, were called to end the party but were confronted by hundreds of teenagers, some throwing beer bottles at police cars and damaging property.

The handler presented one twin's scent to the dog and then told it to go find the matching scent in a lineup of seven jars, which included the other twin's scent.

Around 7.20pm, five riot police, and a line of officers with dogs, emerged from Royal Exchange Square, a pedestrian side street.

A helicopter and dog teams were used to scour houses, parking areas and open spaces, but no one was found.

The suitability of such tactics - including the use of dogs and the numbers of officers involved - should now be coolly examined.