LONDON — A week before the country faces a potentially chaotic departure from the European Union, debate in Britain’s House of Commons was interrupted on Thursday by something even more urgent: a leak that sent a torrent of water into the press gallery.

Justine Greening, a Conservative lawmaker, was concluding a speech about an anti-tax-avoidance measure when she was interrupted by the sound of water pouring down inside the chamber.

“I want to finally finish my comments with a leaky roof in the background,” she said on Thursday afternoon, amid laughter from fellow lawmakers.