Their rag-tag display of banners are viewed by many as an unsightly blemish. But the former foreign secretary has some sympathy, if not for the manner of the peace protest, then for the anti-war sentiment behind it. The Tory leadership contender was among a minority of Conservatives to oppose the Iraq war.
He believes the decision of the Government and opposition to "whip" their MPs through the lobbies in support of invasion, was "inappropriate".
"It was a crucial issue of national importance. No general election had been fought on the subject. And yet the House of Commons and all parties expected Members of Parliament to follow a party line. Now some refused to do so. I wasn't an MP, but I would have refused if I had been," he says.
Sir Malcolm spent eight years outside the Commons after losing his Edinburgh seat in the 1997 election. During that period he says he witnessed the "authority" of Parliament diminished. He believes the stranglehold of the whips is partly to blame.
"We do far too much whipping," he declares, rather excitedly. "The Government of the day uses three-line whips and two-line whips on almost every issue." He argues that the erosion of the "personal authority" of MPs under Tony Blair has reduced public trust in politics.
In an obliquely coded criticism of those within his own party who admire New Labour, Sir Malcolm warns against trying to mimic Blairism in a desperate bid to win power. "There is no need to lurch to Blairism or the centre ground," he says. His remarks will be interpreted as a thinly veiled attack on David Cameron, his leadership rival, who is said to see Tony Blair's re-shaping of Labour in 1994 as a model for regaining power.
In a further dig at Mr Cameron, who is often defined as a moderniser, he suggests that the thinking behind the new-fangled political tag may not be entirely Tory. "I don't use the term moderniser because I start as a very convinced Tory," he says, pointedly. "I do not feel any need to look to other non-Conservative ideologies for my political sustenance."
With devastating understatement, he goes on to suggest that the concept of modernisation may be rather nebulous. "The objective is not modernisation. I don't know what that means," he adds. "I don't find it a particularly meaningful alternative."
Away from Parliament, the Scottish lawyer enjoys going for long walks with his energetic cocker spaniel Rufus - which coincidentally was also the name of Winston Churchill's dog.
And it is to Churchill's one-nation tradition that Sir Malcolm says the party must look if they are serious about winning back power. "The one-nation tradition is based on a Conservative commitment to social justice, to equality of opportunity and personal freedom," he says. "And to realising that the Conservative Party is best when it is perceived to be working for the national interest."
Sir Malcolm admits one-nation Conservatism "needs to be brought up to date" but believes it is as "fundamentally as sound as ever". He says the credo, originated by Disraeli, would appeal to millions of floating voters who may be instinctively conservative, but have failed to back the party since 1997.
Candidly, he says the British public have not been "comfortable with what the Conservative Party has been offering" in the past eight years.
"The perception has been of a party preoccupied with immigration, with Europe, with issues of that kind," he says. He disagrees with Theresa May's assertion that the Tories are perceived as the "nasty party" and - biting his lip to prevent him using a harsher phrase - says her choice of words was unfortunate.
But Sir Malcolm criticises the Tories for being "so preoccupied with the very serious problem of crime" they have forgotten "there is a strong tradition in the Tory party of personal freedom and protecting people from the power of the state".
He issues "a gentle reminder to my own party that we have a strong civil liberties position which occasionally has been lost sight of". Sir Malcolm says he has "no problem about being beastly to criminals". But, he says, law and order should also mean that "respectable law-abiding citizens are not harassed by the state or the agents of the state".
He says it is "deeply disturbing" that Tony Blair "has removed some of the traditional safeguards" to protect individuals from harassment and being accused of crimes they did not commit.
To re-enter government, Sir Malcolm says the Tories must also "re-engage with the public", including ethnic minorities. "We have not been doing that very well for a few years," he says.
He is critical of the party for failing to gain any political ground since 1997. "We need to ask ourselves some pretty difficult and painful questions about how we have allowed such a situation to arise," he says.
"Our share of the popular vote at the last election was unchanged as it was 10 years earlier and that is not good enough."
He warns MPs not to condemn the party to "permanent opposition" by choosing a new leader who has no appeal outside the party. He says the Tories are not about "wallowing in opposition but public interest and government". If this message has not hit home, he cautions, the Tories are "not a serious political party".
"We ought to be choosing a potential prime minister who is going to be able to compete with Gordon Brown who will be Prime Minister in the latter part of this parliament," he says. "And he is a very formidable opponent."
There is little doubt that Sir Malcolm, who was in the Cabinet for 11 years, has the wit and political experience to take on the Chancellor at the dispatch box. But his critics say he lacks support among Tory MPs to make it to the final shortlist of contenders.
He parries this suggestion with good humour, declaring the contest "hasn't even begun yet" and that "around 70 MPs" have not yet decided who to support.
But has he got the backing of the 10 MPs he needs to progress in the leadership race? Sir Malcolm laughs nonchalantly, if a little nervously, declaring "Oh, I am not worried about that."
But with Kenneth Clarke and David Cameron occupying similar political territory, the Conservative left-field is beginning to look crowded.
There has been recent talk of a pact between Mr Clarke and Mr Cameron to beat David Davis, the right-wing front-runner. But Sir Malcolm dismisses such talk of a "dream ticket" as a "dream nightmare".
"I think dream tickets are dream nightmares because the public are not impressed," he says. "One of the most unwise decisions of a previous campaign was when Ken Clarke and John Redwood formed a curious pact that did not take either of their aspirations forward."
Sir Malcolm says he would not "rule out" an eventual deal with another candidate, but adds, "I don't think that is going to happen. I certainly don't want to be involved in that at the moment."
Critics of the MP for Kensington and Chelsea say he is too old to lead the Conservatives.
Sir Malcolm looks shocked at the suggestion. As if to prove he is quite as energetic as any of his rivals, he almost jumps out of his seat, declaring he has been prematurely aged by the press. "I am the same age as David Davis, people don't realise that," he proclaims, before adding: "That is not strictly correct David is 57 and I am 59. People think I am the same generation as Michael Howard and Ken Clarke because I was in the same cabinet.
"I was a sort of child prodigy," he adds with a smile.
In fact David Davis is 56, not 57, but there is not much more than two years between them. And, unlike his right-wing rival, Sir Malcolm entered the Cabinet at the age of 39 and served as Foreign Secretary until the Tories lost power.
Is it a hankering for another seat at the Cabinet table (preferably the top one) that is driving him on? "I have been Foreign Secretary. I have been Defence Secretary, I don't have to aspire to be a cabinet minister again," he says. "I have done that, got the T- shirt."
So with a CV as grand as his, what is motivating him to run at all? "I am involved in this competition because I passionately believe that only a Conservative Party that recovers its reputation as a moderate, practical party has any prospect of winning the next election," he says.
Then, with a cursory glance at the war protesters outside, he adds: "I desperately want to see a Conservative government. The last eight years have been very wasted years".
* BORN: 1946 in Edinburgh
* EDUCATED: George Watson's College; Edinburgh University (law; political science)
* FAMILY: Married to Edith, one daughter and one son
* CAREER: 1967: Teacher at a university in Southern Rhodesia (now Zimbabwe)
1969: called to the Bar; Advocate
1974: MP for Edinburgh Pentlands
1979: Junior member at the Scottish Office
1983: Minister of State at the Foreign Office
1986: Secretary of State for Scotland
1988: First British government official to arrive in Lockerbie after the bombing of Pan Am Flight 103
1990: Minister of Transport
1992: Secretary of State for Defence
1995: Secretary of State for Foreign and Commonwealth Affairs
1997: Loses parliamentary seat
May 2005: Shadow Work and Pensions secretary; MP for Kensington and Chelsea
14 August: Declares himself contender for Tory leadershipReuse content