Could a new mayor break up a police force?
BBCConcerns have been raised over the impact plans for a Thames Valley mayoral authority could have on policing.
Matthew Barber, Conservative police and crime commissioner for the region, has warned the move could lead to the costly break-up of Thames Valley Police, as the proposed mayoral area does not match the force's boundaries.
Last month the government said it was in the final stages of agreeing a mayoral authority for the Thames Valley as part of 10 new devolution deals across England.
Supporters say mayors would empower local areas, bring more money and control over transport, housing and skills, and give people a single figure to hold to account.
Barber said he was sceptical of the move, which he fears, alongside government plans to significantly reduce the number of police forces in England and Wales, could put the future of Thames Valley Police at risk.
"It could easily, with what we're seeing about the mayor, see the breakup of Thames Valley Police as it is at the moment," he said.
"That could mean millions of pounds in costs wasted on a restructuring. It could mean important assets like control rooms being lost to other neighbouring areas.
"And what the public really want is that money on policing being spent on policing on the ground to cut crime now."
He said £100m had already been taken out of operational policing nationally this year to fund police reform.
Barber also questioned the proposed area, which would cover Oxfordshire, Berkshire and Swindon but not Buckinghamshire.
"The addition of Swindon, the exclusion of Buckinghamshire just doesn't fit with a lot of other bits of the public sector, it doesn't fit with the NHS, it doesn't fit with policing," he said.
He added that the government and local leaders had not set out what the benefits would be for residents, and said he had concerns about mayors being able to borrow against local tax income.
"Ultimately, that's just more state borrowing, but on the back of local taxpayers," he said.
But despite his concerns, Barber has not ruled out standing for the position himself.
He said he had no plans at the moment to stand, adding: "I guess you'd never say never in this life."
The government has been approached for comment.
What is being proposed?
The 13 councils involved say the government has proposed £9.1m of funding as the plans are developed.
A consultation is planned for the new year, with a formal proposal going to government in spring and mayoral elections expected in 2028.
Mayors would typically control aspects of transport, skills, housing and local infrastructure, and would receive a share of business rates from next year and income tax from 2028.
What would it mean for policing?
Police and crime commissioners are due to be abolished in 2028, with their powers passing to mayors where possible.
Separately, the government plans to significantly reduce the number of police forces in England and Wales, with an independent review led by Lord Hogan-Howe looking at how they should be structured.
Thames Valley Police covers Oxfordshire, Berkshire and Buckinghamshire, while Swindon is policed by Wiltshire Police.
Some council leaders backing the plans, including Oxfordshire County Council's Tim Bearder, have also warned that excluding Buckinghamshire could have implications for policing and the NHS.
Barber's office has previously warned that Thames Valley Police could become part of a larger South East force.
What do supporters say?
Chancellor John Healey said the deals would bring "new powers to the people who know their areas best".
Oxford City Council leader Susan Brown has previously described the plans as "a once-in-a-generation opportunity".
Liz Terry, the leading of Reading Borough Council, said the authority would "unlock enormous benefits for residents in Reading".
Swindon Borough Council leader Gary Sumner called the announcement "a landmark moment", and Swindon leaders have argued the town's brownfield sites could help boost housebuilding across the area.