The lanky man weaving between tables of coffee-drinking MPs goes largely unnoticed, but as Jeremy Corbyn's chief spin doctor, Seumas Milne is a man of real significance.
As executive director of strategy and communications, he is widely seen as the leading general in Mr Corbyn's team.
And Mr Milne was in the spotlight this week after claims surfaced in the Sunday Times that he, and other colleagues in Mr Corbyn's office, had failed to take seriously Labour's antisemitism crisis.
The allegations were said to have been included in a detailed submission made by Joshua Simons - a 23-year-old Jewish policy adviser in Mr Corbyn's senior team until April - to Shami Chakrabarti's investigation into Jew-hate in the party.
A friend of Mr Simons told the newspaper Mr Milne had repeatedly questioned the aide about his Jewish background and his views on Israel.
The Sunday Times also claimed Mr Simons's evidence included an account of "flippant disdain" displayed by Mr Corbyn's colleagues ahead of his meeting with the Board of Deputies in February.
The newspaper also said that the submission claimed when Ken Livingstone toured television studios in April alleging Hitler supported Zionism, a figure in Mr Corbyn's office made a comment about a "Jewish conspiracy".
There was no mention of Mr Simons's claims in the report produced by Ms Chakrabarti in June.
A spokesman strenuously denied the claims against Mr Milne this week, describing them as coming from a "disgruntled former member of staff".
Another former adviser, Harry Fletcher, told the JC last month how Mr Corbyn and those around him had a "deep-seated problem" with Israel and had ignored warnings about the worsening relationship with the Jewish community.
A gap year in Lebanon is said to have laid the foundations for Mr Milne's interest in the Middle East and preoccupation with Israel. He once told a rally Hamas "will not be broken, because of the spirit of resistance of the Palestinian people", and urged the government to impose an arms embargo and sanctions against Israel.
Educated on a scholarship at the exclusive Winchester College boarding school, Mr Milne graduated from Balliol College, Oxford, where he read politics, philosophy and economics. His father, Alasdair Milne, was a BBC director general.
An admirer of Russia, Mr Milne's attendance alongside Vladimir Putin at a conference in Sochi in 2014 reportedly caused concern at the Guardian, where he worked for more than 30 years before he went on leave to assist Mr Corbyn.
He has a track-record of controversial statements and his thoughts on armed resistance, the September 11 terror attacks and a variety of revolutionary politicians have stirred the anger of his critics. In 2004, under his leadership, the Guardian's comment section published a piece by Osama bin Laden.
When Ms Chakrabarti met journalists to launch her antisemitism inquiry the previous month, Mr Milne sat tucked away at the side of the room.
He was there again weeks later at the shambolic launch of her report, prowling the fringes of a hall packed with hard-left pro-Corbyn activists. Again, few would have noticed his presence. But his influence will continue to be felt throughout the Labour Party for the foreseeable future.
