Married office worker Graham Rycraft, 51, used a "secret" phone to talk to children online without attracting the attention of his wife or colleagues.
He often limited use of the phone to the hours of 8am and 4pm when he would be in work, where his covert messaging would attract less attention.
Rycraft began speaking online last September to who he believed was a 13-year-old girl, but was actually a police officer using an online persona to target predatory sex offenders.
He initially claimed he was a 15-year-old boy and then sent vile images of child abuse, before admitting that he was an adult and continuing to groom the 'child'.
Rycraft arranged to meet the 'child' - but went to great lengths to keep his identity hidden.
He was arrested in a phone box near to his office in Fitrovia, central London, on September 5th, 2018, having just confirmed to the 'child' where he wanted her to meet him.
Police found his 'secret phone' which revealed the true extent of the indecent images that he possessed and shared.
When detectives searched his workplace they found a bag containing condoms and Viagra.
Rycraft, of Stratford, east London, was charged the following day and remanded in custody.
He was found guilty of attempting to meet a child following sexual grooming, attempting to engage in sexual communication with a child, attempting to cause a child to watch a sexual act, distribution and making indecent images of children following a trial in May.
Rycraft was sentenced at Snaresbrook Crown Court on Friday to six years' imprisonment, with a further four to be served on licence.
During sentencing the judge assessed Rycraft as a "dangerous" offender and a risk to children.
Senior crown prosecutor Negeen Momtahen said: "Rycraft pitched himself online as a 15 year old boy from Camden to target vulnerable children and teenagers.
"He used what he believed were thorough methods to conceal his criminal activities, using a secret phone, a public phone box, and keeping Viagra and condoms in his desk at work.
"In this instance, the subject of Rycraft's attention was thankfully an undercover police officer, but had he been successful his actions could have led to the abuse and suffering of children.
"This conviction sends a clear message to similarly-motivated criminals that this behaviour will not go unpunished."
Det Insp John Halford, of the Met's Central Specialist Crime, said: "Rycraft is a calculated and callous man who sought to groom children for his own sexual gratification, taking steps to ensure his own security in the assumption that he would not be caught.
"In actual fact he had encountered officers carrying out a proactive operation aimed at bringing those who seek to exploit and abuse children to justice.
"He will now spend years behind bars, where he belongs."
He added: "I am proud of the dedicated team of officers involved in this operation who have worked so hard to put a dangerous offender in prison and are continually working to safeguard and protect the children of London."