When Caroline Farrow, a Catholic commentator, and transgender rights campaigner Susie Green, agreed to take part in a television debate about a controversial Girl Guides policy, producers would have expected differences of opinion.

But while the conversation on screen was certainly heated, it was what happened off-air when the pair continued the debate on Twitter that resulted in a six-month-long police investigation.

Mrs Farrow, a mother of five with strong religious views, allegedly used the wrong pronoun when referring to Ms Green's transgender daughter.

Ms Green was so angered by what she described as a "distressing and spiteful" attack that she lodged a formal complaint with Surrey police.

On Monday night, they contacted Mrs Farrow and asked her to attend a voluntary police interview.

The response by a police force which, like all others, is struggling to cope with violent crime and knife violence, will raise eyebrows and further fuel the debate around police priorities.