patrick rock
Patrick Rock, 62, quit his post a day before being arrestedSteve Back / Barcroft Media

Downing Street is under mounting pressure to explain its prolonged silence over the arrest of one its senior aides.

Patrick Rock was arrested three weeks ago after being accused of an offence related to child abuse imagery. The National Crime Agencyhas been investigating his office and IT system inside No 10.

But David Cameron only made a public announcement about his arrest on Monday (3 March) after he was quizzed by a national newspaper.

Officials also revealed that Rock was subject of a formal sexual harassment complaint allegedly involving a woman civil servant. She moved out of No 10 to another department after the case was examined by chief of staff Ed Llewellyn.

Rock wasborn Patrick Robert John Rock de Besombes into a family of European aristocrats. His paternal grandmother was a D'aigneaux, from a noble French family who originated in Normandy and boasts a coat of arms.

As a teenager he went to Jesuit Stonyhurst College in Lancashire and won a scholarship to Worcester College, Oxford, where he studied history.

When he graduated he went to work for Margaret Thatcher as political correspondence secretary.

But despite working for 30 years for the Conservatives he repeatedly failed in his goal to become an MP.

He fought the Woolwich East election in 1979, aged 28, but lost despite increasing the Tory vote.

He was then selected in a by-election to defend Tory stronghold Portsmouth South in 1984 after losing the Crewe and Nantwich election a year earlier.

It was during the Portsmouth South campaign that he was described as "likeable and energetic but slightly wet behind the ears". He made a major blunder when he spoke on TV about a hospital that was not in the constituency.

His defeat by the Liberal SDP Alliance left him "pale with shock", local newspapers reported. It was also labelled as the biggest election upset for years and a "great surprise" to Thatcher.

The following year he went to work at the Conservative Research Department and then as special adviser to Cabinet ministers in the Department of the Environment and then the Home Office, where he met David Cameron.

Rock again failed in his bid to become an MP in 1990 when he tried to represent the Tory seat of Devizes in Wiltshire.

He went on to work for Chris Patten in Brussels, with the responsibility for the western Balkans, before Cameron brought him back into government in 2011 as a special adviser in the role of deputy director of policy. As part of that role he worked with the government in 2013 on proposals to introduce internet filters to stop children accessing porn on computers.

Before he was arrested on 13 February he was widely tipped to become a peer.

He is not married and is 62. He lives in a £500,000 flat in Parsons Green, west London.