Matthew Smith, 34, was arrested by National Crime Agency officers at his home in East Dulwich on Sunday 6 November.
Smith was charged with causing or inciting the sexual abuse of a child under 13, distributing indecent images of children (IIOC) in category A, and three counts of making IIOC in categories A-C.
He pleaded guilty to all five counts on Wednesday and is due to appear at Southwark Crown Court for sentencing on a date to be fixed.
This remains a live investigation, with early indications of significant online offending and international lines of inquiry.
Tony Cook, NCA Head of Child Sexual Abuse investigations, said:
“These guilty pleas are a significant step in what is an ongoing, complex investigation. Child sex abuse perpetrated online and across borders is a substantial threat to the UK, and the NCA is dedicated to investigating in these challenging spaces in order to safeguard children and pursue the highest risk offenders.
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