The phrase "parliamentary estate" refers to the area of land and buildings where a country's parliament conducts its operations. It includes the parliament building and other related structures. Full definition
Parliamentary estate announces plan to ban plastic bottles and trial 25p levy on disposable cups (businessgreen.com)
The reality is that Gregory was just one of the honours brokers of the day, brazenly conducting his business from a house on the parliamentary estate, but with rivals in the Unionist and Liberal parties. (totalpolitics.com)
Perhaps something terrible had happened outside the parliamentary estate (on the rare occasion a researcher leaves Westminster)? (totalpolitics.com)