Lord Cameron of Chipping Norton sworn in at Westminster
The former Oxfordshire MP and former Prime Minister quit the Tory frontbench after the General Election last month.
Former foreign secretary Lord Cameron of Chipping Norton has sworn the oath of allegiance to the King at Westminster following the return of Parliament.
Many peers had already made the pledge at the despatch box ahead of the recent King's Speech.
Lord Cameron had resigned from Rishi Sunak's frontbench after the Tories crashed to their worst election defeat at the start of the month.
The Conservative peer's deputy at the Foreign Office Andrew Mitchell MP has become the shadow foreign secretary.
Announcing he was stepping back from the parliamentary frontline, the former prime minister said at the time it had been "a huge honour" to serve as foreign secretary and pledged to continue to support the party and help rebuild "from the very disappointing election result".
Lord Cameron was appointed to the Cabinet last year in a shock return for the former Conservative leader, who resigned after the Brexit vote in 2016.
As he was not an elected MP he could not appear in the House of Commons and so instead was subjected to a special monthly question time in the House of Lords.
Earlier, two non-party political peers took their seats on the red benches.
Dr Alexandra Freeman, a filmmaker and expert in the communication of science, and British engineer and academic professor Lionel Tarassenko, had been recommended by the independent House of Lords Appointments Commission.
Both will sit on the independent crossbenches.
Baroness Freeman of Steventon, who won a Bafta for Walking With Beasts Interactive and was series producer of Trust Me, I'm a Doctor, also helped communicate the evidence around Covid-19 transmission and the benefits and risks of vaccination during the pandemic.
Lord Tarassenko is internationally recognised for being amongst the first to apply machine learning to real-world problems.
Most of his research has been concerned with the application of AI to safety-critical systems, working on jet engine health monitoring with Rolls-Royce and on patient monitoring and treatment in the NHS, to improve outcomes from intensive care to community settings.
Both wore the traditional scarlet robes for the short introduction ceremony in the upper chamber where they swore allegiance to the monarch.