A new offence to cover lone individuals planning non-terrorist mass killings should be considered in the wake of the Southport attacks, the UK's terror watchdog has said.

Jonathan Hall KC said it was "horrifying" officers couldn't intervene despite knowing Rudakubana planned mass killings.

The watchdog’s review commissioned by the Home Secretary to examine terror legislation in the wake of the Southport murders was published on Thursday, where he also warned against changing the terrorism definition.

A gap in the law prevented the Southport killer being arrested before he carried out the horrific attack last summer, a watchdog has said.