Pickles is the man who kept telling us that "the House of Commons runs like clockwork".
Sky News political correspondent Jon Craig said Conservative sources had told him the two men and one woman were journalists.
"Police broke up what the Conservatives have told me was a domestic," he said.
"There are cells in the House of Commons and they could be held there for some time.
"My understanding is that these people are under arrest still.
Craig added that the Tory chairman was likely to be hugely embarrassed by the incident.
Later. The Northern Echo adds:
Police used CS spray to break up a fight in the Houses of Parliament tonight, sources said.
It is understood that guests of an official passholder began scuffling shortly after 9.15pm.
Police officers were unable to stop them fighting and one used their CS spray. According to reports, three people were arrested.