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Clive Ruggles, whose 24-year-old daughter Alice was stalked and then murdered by her ex-boyfriend in Gateshead in 2016, said he was "getting increasingly exasperated" that SPOs were so little used five years after being introduced.

The Alice Ruggles Trust was part of the campaign to get the orders passed into law.

"This is what we fought for," Mr Ruggles said.

Both Cohen and soundman Brian Ruggles have been with Joel for more than 50 years.

But one leading critic of differential privacy, University of Minnesota demographer Steven Ruggles, says the study supports his view that the agency should return to swapping.