John Alford, a one-time fixture on British television, has been convicted of sexual offences involving underage victims and is facing prison, in a fresh blow to a career already fractured by a high-profile tabloid drugs sting two decades ago.

Alford, 53, rose to national fame as a likeable presence on children’s drama Grange Hill and the firefighter series London's Burning in the 1980s and 1990s. He also recorded three top-20 singles in the mid-1990s, including a cover of the show tune "Smoke Gets in Your Eyes" and the anti-drugs single "Just Say No," which reached number five in the charts when recorded with members of the Grange Hill cast.

Alford's public standing was severely damaged after he was the subject of a drugs sting by the News of the World involving undercover reporter Mazher Mahmood, later dubbed the "Fake Sheikh." Mahmood promised Alford a part in a Robert De Niro film as part of the operation, which led to Alford being convicted of supplying cocaine and cannabis. He served six weeks of a nine-month sentence and has said the episode effectively ended his acting career and left him dependent on benefits.

In the latest developments, court proceedings found Alford guilty of having sex with a 14-year-old girl and of sexually assaulting a 15-year-old girl at the same party, according to court accounts. The convictions include findings that he had sexual contact with a 14-year-old in a garden and in a toilet, and performed a sex act on a 15-year-old later at a Hertfordshire home belonging to a third girl who was friends with the victims. Prosecutors said the incidents occurred at the same gathering.

Alford has denied some aspects of the authorities' account and has told police and others that he was the target of a blackmail plot. The court's verdicts, however, resulted in criminal convictions that now expose him to a further custodial sentence.

The two episodes—the earlier drugs conviction stemming from a tabloid sting and the recent sexual offence convictions—outline a fall from prominence that has unfolded over decades. During his peak, Alford was widely recognised by viewers of children’s television and had sustained media attention as a pop performer associated with anti-drug messaging. After the News of the World operation and subsequent prison time, he struggled to rebuild a mainstream acting career.

The undercover reporting methods used by Mazher Mahmood have been subject to broader scrutiny and criticism, and Mahmood himself has been described in media reports as "disgraced" amid investigations into his journalistic practices. Those controversies have fed ongoing debates about tabloid journalism's methods and the consequences for those targeted.

Legal authorities will determine Alford's sentence for the recent convictions following the usual sentencing process. The criminal record and the public nature of the cases are likely to further complicate any attempts at a career revival and will add to a personal history already marked by public controversy and prior imprisonment.

Representatives for Alford did not immediately respond to requests for comment. The News of the World ceased publication in 2011 amid a separate phone-hacking scandal that involved other practices by the tabloid press.

Alford's case underscores the long-term impacts that high-profile criminal cases and tabloid interventions can have on public figures, and it raises questions about the intersection of celebrity, media practices and the criminal justice system.