A former police constable with "a dark side" of sexually fantasising over young girls has been jailed for three-and-a-half years.

Married father-of-one Nicholas Pool, 29, was exposed as a paedophile during conversations in an internet chatroom with an undercover police officer who was pretending to be 12 years old.

Pool, from Penrith, Cumbria, gave his real age to the "girl" and ironically warned her "a lot of pedos in here be so careful" before he later suggested they meet up to "teach you about sex".

He was arrested in December 2016 and further offences came to light when his laptop was examined and found to contain indecent images of pre-pubescent girls, Carlisle Crown Court heard.

Similar online conversations were also uncovered with other individuals purporting to be young girls, including one exchange in which he said wanted to get a 12-year-old pregnant.

Another internet user, who said she was a mother from Canada, sent Pool images of what she said was her eight-month-old daughter and five-month-old baby, and discussed "sustained and repeated rape fantasies" of extremely young children.

Pool, a serving officer based at Barrow police station at the time of the offences between 2013 and 2016, was dismissed by Cumbria Constabulary in February after he entered guilty pleas.

Following sentencing on Friday, the force said the defendant had "brought shame" upon himself and the constabulary.

In mitigation for Pool, his barrister Michael Rawlinson said: " He has, effectively, a fractured personality.

"He has a real life, a married man with a child who was a serving police officer.

"And he has a dark side to his personality. A fantasy life which involves inappropriate and very disturbing fantasies about young children."

But he said that those who knew him well had testified in character references that he was "hard-working and generally a good person to have around".

He said a remorseful Pool had "destroyed" his real life with the end of his career and the imminent end of his marriage after his wife filed for divorce.

Pool, from Newton Rigg, pleaded guilty at earlier hearings to nine counts of attempting to incite a child to engage in sexual activity, three counts of making indecent images of a child, one count of possessing an indecent image of a child and one count of publishing an obscene article.

Robert Wyn Jones, prosecuting, said that Pool began communicating with the undercover officer in an internet chatroom for teenagers in November last year - a chatroom in which Pool claims he himself had been sexually groomed as a teenager.

The exchange of sexualised messages progressed to chats on Skype, in which the defendant said: "If you want I could meet you and teach you about sex. We could have sex too.

"I've always wanted to have a GF who has never had sex or anything before ... cos then they don't have any bad habits and I could show them exactly what I like."

Following his arrest, a total of 48 indecent images of young girls were discovered on his laptop.

Among his online conservations was with someone who said she was an 13-year-old girl who Pool asked for oral sex.

He also said he wanted to have sexual intercourse with her, but it was "bad of him as she is a child", said the the prosecutor.

Mr Wyn Jones said: "He then continues and says 'I need to have sex so bad. I would f*** the next girl I see'."

Pool told another online user - said to be a 12-year-old girl: "I want to get a little girl pregnant. Please say 'I want your baby, I'm only 12 but I want to get pregnant to you'.

He went on to ask a friend of the "girl" aged 10 if they too could have sex.

Mr Wyn Jones said: "He then asks her 'when we have a baby girl, will she have sex with me too?'"

Defending Pool, who has a one-year-old child, Mr Rawlinson said that over a considerable period of time his client had not acted upon "clear fantasy roleplay and ideas expressed during his internet life".

Sentencing the defendant, Judge James Adkin said the prosecution had not been able to discount that those who he communicated with - apart from the undercover officer - were not children but adults with "similar deviant proclivities".

He said that the progression of the conversations with the undercover officer was "manipulative".

Cumbria Police's Deputy Chief Constable Michelle Skeer said: "Nicholas Pool has brought shame upon himself and the Constabulary, and he has rightly been sentenced today for these serious crimes.

"This case highlights that predators can be from any walk of life, and that no matter who you are or where you work, we will seek to ensure that you are brought to justice.

"As well as being in possession of some horrific images, Nicholas Pool was conversing with young girls in a sexualised manner, demonstrating how important it is for parents to be aware of who their children are speaking to online.

"Many young people will use the internet and social media. Consequently there is a realistic danger that your child is speaking to someone online that they do not know.

"We will continue to work with partner agencies to promote awareness of internet safety and ensure that these offenders are brought to justice."