No charges are to be brought against two men arrested over a fire which destroyed Hastings Pier, the Crown Prosecution Service said today.
Up to 95% of the East Sussex pier was damaged after the blaze broke out in the early hours of October 5 last year.
An 18-year-old man and a 19-year-old man, both from St Leonards, were arrested shortly afterwards but the CPS said it has now been decided that there is not enough evidence to charge them over the fire.
Tim Thompson, head of the CPS Brighton trials unit, said there was evidence that both men had trespassed on the pier at the time but it was not possible to tell if one or both could have been responsible for starting the fire.
He said: "There is evidence to place both suspects, as trespassers, on the pier at the material time.
"There is evidence that a fire started through some human act at the time they were on the pier.
"We are left in the position where we cannot show how the fire was started and cannot show that the human act must have been a criminal act.
"We cannot show that there was or must have been any kind of joint plan.
"We have no admissible evidence to show which of the two suspects might have been responsible.
"We cannot prosecute on the basis that one or other of the two suspects might have been responsible; we can only prosecute where there is enough evidence against an individual."
The nature of the Victorian structure and the extent of the fire made it "a particularly difficult crime scene", he said.
"I appreciate there will be concern that no-one is being prosecuted.
"It is disappointing that we are not able to mount a prosecution in a case that is of considerable local interest but it is our responsibility to only bring prosecutions where there is sufficient evidence for a realistic prospect of conviction."
If new information comes to light the case will be reconsidered.
The pier, which was designed by Eugenius Birch and opened in 1872, became derelict in recent years and had been closed since 2006.
At the height of the blaze, around 55 firefighters with eight engines were trying to extinguish the flames, watched by scores of locals, some dressed in their pyjamas.
In the days afterwards people left dozens of colourful ribbons, flowers and notes on its gates.
Campaigners from the Hastings Pier and White Rock Trust, who had been battling to restore it at the time of the fire, have vowed not to give up.
Hastings Borough Council was in the process of taking over the pier in a compulsory purchase after pressure from the trust and following a study which showed it could be made safe for £33 million.
The trust then wanted to take control over the future of the structure and apply for funding as a charity with the aim of refurbishing it with modern attractions.
Commenting on the decision, council leader Jeremy Birch said: "It will be very disappointing for the town if nobody is charged for the arson.
"But the CPS want to make sure they've got the appropriate evidence."
In November, unsafe sections of the pier were dismantled after the council took out emergency powers when its Panama-registered owner, Ravenclaw, failed to take action.
Mr Birch said the council is now awaiting a decision from the Heritage Lottery Fund on May 10 after putting in a bid for £8.5 million in funding to restore the pier.
If successful, the local authority will be able to proceed with the compulsory purchase and pass it over to the trust, he said.
Hastings Pier was the latest historic pier to be hit by fire.
In July 2008, Weston-super-Mare pier was destroyed, while Brighton experienced a devastating year in 2003 with its West Pier suffering two major blazes within two months after parts of it had already crumbled into the sea.