A 28-year-old white British man from Rotherham, South Yorkshire, was arrested on suspicion of murder on Saturday. He has since been rearrested on suspicion of commission, preparation or instigation of acts of terrorism.
The head of national counter-terrorism policing, Laurence Taylor, said: Building on the progress made by our colleagues in Devon and Cornwall police, we now have new information and evidence that means counter-terrorism policing is now leading the investigation.
https://www.theguardian.com/uk-news/2026/jul/13/ann-widdecombe-counter-terrorism-police-investigation
The timeline, if they have the time of the attack correct, indicates he drove straight to her house from Yorkshire (given the weekday morning rush hour traffic he'd have encountered at the start, I'd suspect a bit of moderate motorway speeding to make it in that time, in which case they may have traffic cameras too):

So that does look like a pre-mediated attack, rather than, say, an opportunistic burglary that turned violent.