Officers investigating a small fire that occurred at the Palace of Westminster in July have arrested a 32-year-old man on suspicion of arson with intent to endanger life and criminal damage.
He is currently being interviewed at a south London police station where he remains in custody.
The capital's changing skyline could threaten Westminster's world heritage status.
In a meeting next week, Unesco will consider placing the area surrounding parliament on it's "endangered" list in response to plans for a series of skyscrapers.
“Thisnews is very disappointing because UNESCO have threatened to put theWestminster World Heritage Site on their ‘In Danger’ list if the setting of theWorld Heritage Site was not protected from insensitive development.
"It looks like the Government has failed to do this and we will await news from UNESCO. Loss of World Heritage Site status would be very bad news for the country. It would signal that we are failing in our duty to protect our heritage. "
Thatcher's former cabinet minister Norman Tebbit paid an emotional tribute to his old boss and friend in the House of Commons today.
He spoke movingly of the support she provided his family after he and his wife were injured in an IRA bomb attack at the Grand Hotel in Brighton. He praised her courage and popularity, and reflected on her demise, saying:
"I left her, I fear at the mercy of her friends, that I do regret."
Former Tory minister Michael Howard praised Baroness Thatcher for her taking on the unions and "saving our country." Speaking in the House of Lords he said:
"She saw what needed to be done, and she did it with clarity, with courage, and with conviction."
David Cameron opened the tributes to Baroness Thatcher in the House of Commons.
The Prime Minister said she was an "extraordinary leader and extraordinary woman" who accomplished many great achievements that were viewed by most at the time as "inconceivable" for her gender.
In a glowing tribute lasting more than 11 minutes, Cameron praised to her political skill, her personal tenacity and the unique place she moulded for herself in history. He said:
"The say cometh the hour, cometh the man, will in 1979 came the hour and came the Lady, she made the political weather, she made history and let this be her epitaph: She made Britain great again. "
Labour leader Ed Miliband praised Baroness Thatcher for "breaking the mould".
“At each stage of her life she broke the mould - a woman at Oxford, when there was no a single woman in the university who held a full professorship.
"A woman chemist when most people assumed scientists had to be men, a woman candidate for Parliament in 1950 against the opposition of some in her party in Dartford at the age of only 24, a woman MP in 1959 when just 4% of MPs in the whole of this House were women."
David Cameron has said Baroness Thatcher’s coffin will be “draped with the flag she loved”.
“It is also right that next Wednesday Lady Thatcher’s coffin will be draped with the flag that she loved…
“[The funeral] will be a fitting tribute to a great Prime Minister.”
He described her as an “extraordinary” leader and an “extraordinary” woman.
“It is also right to remember that she spent her whole premiership and indeed much of her life under direct personal threat from the IRA.”
David Cameron has paid tribute to Baroness Thatcher as he opened proceedings on a special debate in the House of Commons.
The prime minister said: “In the long history of this Parliament, Margaret Thatcher was our first and so far our only woman prime minister…
“She defined and she overcame the great challenges of her age, and it is right that Parliament has been recalled to mark our respect.”
The Deputy Speaker of the House in Commons Nigel Evans, has told Daybreak he expects respect from all MPs, no matter what their political beliefs today.
Parliament was recalled from Easter recess for a special session to pay tribute to Margaret Thatcher who passed away this week.
Mr Evans, who was a family friend of the Thatchers, said people needed to pay respect in death, "she was a mother, a grandmother, we've got to think about these things too."