Source Currency: Twenty-sixth edition, published October 2026. Erskine May is the authoritative guide to Parliament’s evolving practice and procedure. For more than 180 years, Erskine May has explained how Parliament works. Regularly cited in the Speaker’s rulings and parliamentary debate, it provides detailed guidance on the practice and procedure of both Houses and the constitutional conventions that govern their business. The 26th edition brings this essential reference up to date with the significant developments since 2019. It captures both the continuing evolution of parliamentary practice and the exceptional challenges of Brexit and COVID-19, explaining how Parliament adapted its procedures in unprecedented circumstances. Coverage of parliamentary privilege, legislative procedure and committees has also been updated and refreshed.