A 21-year-old man who started a blaze which led to the deaths of three people, including a two-year-old boy, has been jailed for seven years.

Sam Benn helped Curtis Bushell to fill a trolley with newspaper and then set it alight in a communal hallway of a block of flats in Chatham High Street.

The fire was so fierce that it destroyed the staircase, trapping the occupants upstairs, and took several crews almost two hours to extinguish.

The bodies of Rikki Sheehan, 27, her son Charlie and her boyfriend Paul Arnold, 34, were found in their second floor, rear flat. It was badly damaged and all three had died of smoke inhalation. Charlie was just one month short of his third birthday.

Benn, of no fixed address, pleaded guilty to three manslaughter charges and was jailed for seven years concurrent on each.

Sentencing him at Maidstone Crown Court Judge Warwick McKinnon described the offences as "heinous".

He said: "What you did together with Curtis Bushell can only be described as mindless, homicidal vandalism, reckless, dangerous and wicked in the extreme with the result that three quite innocent people have had their lives snatched from them and in the most horrific circumstances.

"What is left behind is a trail of devastation, bereavement, outrage and sheer bewilderment at the senselessness of it all."

Judge McKinnon added that he gave Benn full credit for his guilty pleas and had considered his young age, low intelligence and the fact he was to give evidence against his co-defendant.

"I am prepared to accept that may well have been a contributing factor and instrumental in leading Curtish Bushell to ultimately admitting his guilt in this affair."

After a hearing on Wednesday to assess whether Bushell was fit to plead, the 18-year-old pleaded guilty to the same manslaughter charges. An interim hospital order has been made under the Mental Health Act and he will return to court for sentence on August 4.

The court heard that on the night of March 18 last year Benn and Bushell had met up by chance outside Pembroke Court in Chatham. They headed for Rochester, passing the main door to the flats, which was often left unlocked.

Nicholas Wood, prosecuting, told the court that a room under the stairs used to store rubbish had often been used by homeless people, including Bushell. However, following complaints by residents Moat Housing Association had put a lock on the room door.

On the night of the fire, Benn and Bushell’s movements were captured on CCTV. They were seen going into the building at 12.45am and leaving a few minutes later.

Mr Wood said the pair saw the Staples trolley in the hallway, which was also littered with junk mail and free newspapers. Referring to Benn’s witness statement he told the court how the pair each rolled up a newspaper and put it in the trolley, which was made out of both metal and plastic.

"Bushell asked if he could have my lighter," Benn stated. "I asked what he was going to do and he said he was going to light it. I gave it to him.

"He lit one of the corners and the newspaper caught light. We waited a few seconds to see if it would go out. We were not talking. We just stood there and watched. The fire didn’t go out, it was just small. I thought it would burn out because I thought the trolley was metal."

Benn and Bushell then made there way along the High Street into Rochester. When Benn spotted several fire engines he asked Bushell if it could be to do with the trolley fire. "He said Bushell said he hoped it burnt down," said Mr Wood.

The court heard that no accelerant was used to start the blaze and neither defendant had tampered with the smoke alarm.

Both were arrested together in Rochester High Street at 2.20am. Both had lighters and Bushell, of Balmoral Road, Gillingham, also had matches.

Benn immediately admitted his part in the fire. "It was Curtis," he told police. "I told him I didn’t want to be in trouble but he did it and I ran. I didn’t want anyone to be hurt."

He added that he had never been to the flats before and was "just following Bushell".

Wendy Joseph, defending, said she was mindful that nothing she said would diminish the tragic loss of three lives.

She said Benn was unaware that people were in the upstairs flats and that the fire was not a deliberate act directed towards the victims.

"It was an act directed towards simple arson. It was completely unplanned, it was not his idea and the act was not his act although clearly he was a party to it.

"The wrong that he did was handing over the lighter once he knew it was to be used to light the paper. But what he envisaged was a fire in the trolley that would burn itself out."

The court also heard that Benn had been assessed by psychiatrists and had an extremely low IQ. He had been diagnosed with learning difficulties while at school and at the age of 15 had the intelligence of an 11-year-old.

"This young man is less mature and less able to think through consequences that most people his age," added Miss Joseph.

He had been living in Strood with his father and several siblings but left after an argument and began sleeping rough. He had known Bushell for about 18 months.

The court heard that Bushell had originally denied any responsiblitity for the fire, claiming to have been upstairs when it started. Both were charged with three counts of murder and Benn pleaded guilty to manslaughter at the earliest opportunity.

Miss Joseph said that despite being subjected to "a variety of incidents" while on remand Benn had "wanted to do the right thing" and give evidence against Bushell.

Bushell will appear again before Judge McKinnon at Croydon Crown Court.

Commenting on the case, DCI Mick Judge said: "As far as we are concerned we are pleased for the families that this is now over. The judge’s words 'mindless, homicidal vandalism' sum up this case.

"Two young men carried out an act without thinking what they were doing and which has resulted in the loss of three lives, one of them a child."

DCI Judge added that CCTV had played a crucial role in the police investigation.

All five flats were occupied at the time of the fire. DCI Judge said it was lucky that more people weren’t killed that night.