Four paedophiles who were caught after a reporter answered an obscene graffiti advert on a train toilet door have been handed lengthy jail terms.

Ruth Lumley, 26, a reporter for The Argus, noticed graffiti urging girls between eight and 13 to text a mobile phone number while she was travelling home from work.

Posing as an 11-year-old girl, Miss Lumley who worked on the Chichester Observer at the time, replied to the advert and was sent a series of increasingly sexually explicit messages from a pay-as-you-go mobile phone.

She alerted police and prompted a complex ten-month nationwide investigation that uncovered "horrific" child abuse on eight victims and led detectives to Trevor Haddock, 55, Ian Jones, 43, John Farmer, 68, and Derek Moody, 43.

The four men pleaded guilty to a range of sex offences at Hove Crown Court earlier this month and yesterday were given jail terms ranging from eight years to life.

Judge Anthony Niblett described the men as "morally abhorrent, wicked and harmful to those they abused". He added: "Each of you is a paedophile who poses a continued danger to young children, specifically to young girls."

He said he was sentencing them to deter and protect vulnerable young children from their predatory activities.

Miss Lumley was travelling between Chichester and Brighton when she noticed a scrawled message on the toilet door stating Young girls wanted for sex, aged eight to 13. Text this number only'.

She rang the number twice but it was not answered. However, within 30 minutes she received a text from Jones, which said: "U male or female how old whr u c my number tx bck only."

Miss Lumley sent a text message back, saying "Female, on train, 11" and within minutes received the reply "U up 4 it? R U a virgin or not wht skol u go 2 whr u live tx bk."

Jones then proceeded to send a number of messages to Miss Lumley and when he got no response, he also telephoned her, leaving a voicemail message inviting her to call him, and another text message inciting her to send a naked picture of herself.

Miss Lumley told British Transport Police, who discovered the graffiti on a number of trains in the South-East, as well as in a pub in Euston station, central London.

She said: "It's not the type of message you normally see on the back of toilet doors. I phoned the number but didn't get a reply so I just went home and forgot about it.

"About half an hour later I got a message asking me whether I was male or female, how old I was and where I had seen the message.

"I texted back and said I was an 11-year-old girl and that I saw it on the train. I had never seen graffiti like this before and at first I thought it was a sick joke.

"After I sent back the reply, I got sent about five or six text messages which got more and more sexually explicit. They were really disgusting. It was at that point that I knew I had to phone the police."

Officers seized her mobile phone for analysis over five days during which time more sexually explicit messages were sent.

A British Transport Police officer pretended to be a 12-year-old girl called Amy and arranged to meet a man outside a Burger King in Brighton. Police were laying in wait and arrested Jones. After officers searched his flat and checked his phone records, they discovered calls to Farmer.

Farmer was arrested when police found child abuse pictures on his phone. Two pictures on Jones's phone were taken in his flat and included an image of a third man who police identified as Haddock.

His home was raided and examination of his phone records led to the uncovering of a plan by Haddock to take a young girl to Newcastle so she could be abused by the fourth defendant, Moody, in exchange for cash. However, police stepped in before the deal was completed.

Ringleader Haddock, from Ambleside, Worcester, admitted 14 offences including rape, attempted rape, conspiring to rape and sexual assault.

Jones, of Rowlands Road, Worthing, admitted conspiring to sexually assault a child, attempting to cause or incite a child to engage in sexual activity and four counts of criminal damage with intent to commit a sexual offence.

Farmer, of Pevensey, near Eastbourne, admitted arranging or facilitating the commission of a child sex offence and Moody, of West Midland Road, Newcastle, admitted inciting to rape a young girl.

During the case, it emerged Jones received a 42-month jail term for the attempted rape of a 20-year-old woman in Burgess Hill, in 1984.

It also emerged Haddock charged up to £150 for other men to abuse a young girl he procured, and plied his victims with sedatives, alcohol and cigarettes.

Judge Niblett sentenced Haddock to six life sentences, and said he wouldn't be eligible for parole for at least 12 years. Jones received a life term, with a minimum tariff of ten years, Farmer was jailed for eight years and Moody was handed a life term with a minimum of four years imprisonment.

After describing the four men as "evil", Judge Niblett commended Miss Lumley for her "clear-sightedness" and awarded her £250 from the High Sheriff of East Sussex.

Following the case, Detective Constable Andy Jackman, of British Transport Police, said: "Investigating graffiti attacks is a regular occurrence for the British Transport Police, but it is certainly very rare that such messages lead to us uncovering a paedophile ring that was actively trying to recruit victims on the train network.

"It goes to show that no matter how innocuous something might seem, like a bit of graffiti, it is important to bring your concerns to the attention of the authorities."

Acting Detective Chief Inspector Jeff Lister, of Sussex Police, said: "The sentences today have reflected the serious and horrific nature of the sexual offences committed by these men and the damage they have caused to their young victims."