The founder of homeless charity The Ark Project is planning a protest march through the streets of Windsor after the charity's bus was impounded.
The bus, which is kitted out with beds for ten rough sleepers, was seized yesterday by Thames Valley Police, who said it was being driven without the correct license.
Longsmith, 42, was driving the bus at the time, and yesterday vowed to pay £1,500 to get it out of the impound before driving it straight back to Windsor Castle on Friday morning ahead of Saturday's royal wedding.
Inspector Gavin Biggs, a roads police officer, said the force seized the "commercial vehicle" in the afternoon.
"It was being driven otherwise than in accordance with a licence, a man was reported for the offence and the vehicle was removed," he said.
Longsmith, of Newbury, Berkshire, said police pulled the bus over for not having an MoT, but he proved it was exempt.
Then, he added, they questioned his licence, which he claimed is appropriate for the vehicle. "The bus is in the impound," he said. "We have got to pay £1,500 to get it released."
"We are going straight back to Windsor with it in full force. We are going to park right outside the castle," he added.
talkRADIO spoke to Longsmith this morning, and he said he hadn't been able to reclaim the bus.
"It was impounded yesterday because they believed the bus was a public service vehicle," he said.
"They said if I can get a proper bus driver they’re release it. We went down this morning with a driver, at our own expense, just to be told that a superior officer who refuses to give name and has put a seizure notice on the bus."
He said he did not know what law the bus was currently being held under, and had not been able to obtain any more information from the police.
He added that he'd printed 42 t-shirts bearing the slogan 'Free Lenny' - the nickname of the bus - and was planning to march through Windsor this afternoon.
"We’ve printed up massive banners and we’re going to walk through Windsor with people in the shape of a bus," he said.
"An inspector is telling is there’s nothing we can do.
"To satisfy them we went and got a proper driver now they’ve changed the section they’re seizing it under.
"We’ve had to leave nine homeless people on the side of the road in Windsor."
The Ark Project usually operates in Reading and Newbury, but began taking in Windsor's homeless after Windsor council's Conservative leader Simon Dudley wrote to Thames Valley Police saying rough sleepers should be removed ahead of the wedding.
But, after a backlash, it appears the street homeless have not been removed and the Royal Borough of Windsor and Maidenhead said it has been working with charities to get rough sleepers the help they need.
Inspector Biggs told talkRADIO that the vehicle "will now be retained as part of an on-going investigation to ensure it is roadworthy.
“Once the investigation has been completed, we will be happy to release the vehicle, as long as the correct documentation is in place," he added.