Well known tech start-up investor Stefan Glaenzer has admitted in court to sexually assaulting a female passenger on the London Underground.

Glaenzer will be sentenced on 20 December and has been given unconditional bail while he awaits sentence.

Glaenzer, the former chairman of Last.fm, pleaded guilty to one count of sexual assault, which is said to have been witnessed by police.

The court heard two similar incidents had also been reported. Glaenzer told the court he was a long-term cannabis user and had been on "a drugs binge" at the time of the assault.

As a result of his guilty plea the multi-millionaire investor must now sign the sex offenders register.

Glaenzer's defence barrister Sallie Bennett-Jenkins QC told the court: "This conviction has devastated him personally and professionally. He has lost his good character that he has maintained for his entire life."

Westminster Magistrates Court was told by Glaenzer that he would now seek help for his "drug dependency". But magistrate Jessica Baldwin told Glaenzer his drug use was "an aggravating feature", and could not be seen as "mitigation".

The case has been adjourned for pre-sentence reports.