No, you cannot travel from the UK to France without a valid passport. Since the UK is no longer part of the EU and has never been part of the Schengen Area, a passport is required for all British citizens and most non-EU nationals entering France. As of April 2026, the rules have become even more formalized with the full implementation of the EU Entry/Exit System (EES). This system requires travelers to register biometric data—fingerprints and a facial photo—at the border on their first visit. Furthermore, starting in late 2026, UK citizens will also need an ETIAS (European Travel Information and Authorisation System) waiver, which is an electronic travel permit similar to the U.S. ESTA. While "day trip" IDs or birth certificates were once used decades ago, modern security standards necessitate a biometric passport that is valid for at least three months beyond your intended stay. This applies regardless of whether you are traveling by Eurostar, ferry, or plane. There are no "passport-free" exceptions for standard tourism or business travel between these two nations.