The lord mayor of the City of London, Fiona Woolf, has been named as the chair of the independent inquiry commissioned by the Government into historic child sex abuse.
Ms Woolf, a leading tax lawyer, takes the place of Baroness Butler-Sloss, who stepped down days after being appointed to chair the inquiry in July, after questions were raised over potential conflicts of interest as her brother Lord Havers was attorney general at the time of some of the events to be investigated.
Professor Alexis Jay, author of the recent report into abuse in Rotherham, will act as an expert adviser to the panel, said the Home Office.
The inquiry, announced by Home Secretary Theresa May on July 7, will examine how the country's institutions handled their duty of care to protect children from sexual abuse over a period of decades.
It was prompted by allegations that figures in Westminster and Whitehall were implicated in covering up child sex abuse, and that police and other authorities did not properly investigate prominent offenders such as Jimmy Savile and Cyril Smith.
Mrs Woolf will be assisted by Graham Wilmer, a child sexual abuse victim and founder of the Lantern Project, as well as former deputy chief executive of the National Children's Bureau Barbara Hearn. Ben Emmerson QC will serve as counsel to the inquiry.
Mrs May said: "In recent years, we have seen appalling cases of organised and persistent child sex abuse which have exposed serious failings by public bodies and important institutions.
"These failings have sent shockwaves through the country and shaken public confidence in the pillars of society in which we should have total trust.
"That is why the Government has announced that an independent panel of experts will consider whether such organisations have taken seriously their duty of care to protect children from sexual abuse.
"We are absolutely clear that we must learn the lessons of past failures and the panel will be instrumental in helping us to do this.
"I am pleased to announce today that Fiona Woolf has been appointed to lead this inquiry. I look forward to an update on the panel's progress in due course."
Mrs Woolf, 66, a City solicitor and former president of the Law Society of England and Wales, said: "Ensuring lessons are learned from the mistakes which have been made in the past and resulted in children being subjected to the most horrific crimes is a vital and solemn undertaking.
"I was honoured to be approached to lead such an important inquiry, and look forward to working with the panel to ensure these mistakes are identified and never repeated."
Her first task is to agree terms of reference for the inquiry and finalise membership of its panel, which is due to deliver an interim report to Parliament before the general election in May 2015.
In a written statement to MPs, Mrs May said: "I am confident that Fiona Woolf has the skills and experience needed to set the strategic direction of the inquiry, to lead the work of the panel, and to challenge individuals and institutions without fear or favour to get to the bottom of this issue, and stop it happening again.
"To help her in this role, and to ensure that the inquiry delivers the thorough, robust and independent review that I have promised, she will be supported by a panel of distinguished experts, and will be able to call upon expert advisers as required."
Rochdale MP Simon Danczuk, whose campaigning on the issue fuelled pressure for an inquiry, offered the new chair his support. He called on her to bring "a sense of urgency" to the investigation, which he said had lost momentum due to delays after the resignation of Lady Butler-Sloss.
"I'm pleased the Home Secretary has finally got this moving," said the Labour MP. "Although I would not have looked to high office in the Square Mile to find someone to challenge the establishment, Fiona Woolf is a smart and capable woman and she has my support.
"Britain is in the middle of a child abuse crisis and this inquiry has to be a watershed. It must go to the heart of the establishment and challenge why crimes have been swept under the carpet for so long."
Mr Danczuk said there was "no time to lose", as some alleged abusers are now very elderly and could die before facing justice if the inquiry drags on too long.
He also welcomed the choice of Prof Jay as adviser and Mr Wilmer as a member of the panel. Mr Danczuk said that Mrs May, who called him to discuss the appointments, indicated that she wants other abuse survivors to join the panel.
NSPCC chief executive Peter Wanless - who is chairing a separate inquiry into the Home Office's handling of historic child sex abuse allegations - said: "It's vital that the panel can begin work as soon as possible to get to the bottom of how so many victims were failed in the past by institutions and services responsible for keeping them safe. "
Matthew Reed, chief executive of the Children's Society, said the appointments were "important steps forward".
"It is vital that this independent inquiry tackles the systematic failures that have left some of the most vulnerable children in this country open to abuse," said Mr Reed. "It must also make sure that all offenders and those who covered up their crimes are held to account. The inquiry's momentum must be maintained, but at the same time it must be thorough and comprehensive."
Anne Longfield, chief executive of children's charity 4Children, urged Mr Cameron to establish another inquiry, with a short time limit, to reveal the true extent of child sexual exploitation across the UK, in the wake of the Rotherham scandal.
"4Children believes that the victims of abuse in Rotherham and across the UK deserve action now," said Ms Longfield. "The Government must act now to ensure that children's voices are never ignored again when abuse is reported. The full scale of this systemic failure may never be known, but an urgent and transparent investigation is needed now to ensure this never happens again in Rotherham or anywhere else in the UK."
Shadow home secretary Yvette Cooper said: "It is welcome that the inquiry into child abuse is finally moving forward - almost two months after it was initially announced.
"But we still have no terms of reference for the inquiry and have had no assurances that it will look into current gaps that exist in the child protection system, as well as historical institutional failure. We now need urgent answers on both these issues.
"The most important factor in taking this inquiry forward is to ensure it has the confidence of victims of abuse. Their experiences and the support they need must be at the heart of this major piece of work if we are to better root out abuse and build a child protection system that is fit for purpose. That is why we have made clear from the start this panel needs to involve victims and child protection experts."
Barnardo's chief executive Javed Khan said: " The Fiona Woolf Inquiry must identify whether or not the institutional failures it identifies from historic abuse investigations are still a problem today.
"It is essential that the inquiry has the confidence of victims. They deserve a transparent and impartial process which shines a light into the darkest corners of this country's institutions."