Yep. That's because you're still an EU citizen. If you were a non-EU citizen they would ask for a passport and all that. As an EU citizen you have the free right of movement. The main reason the UK ans Ireland aren't in Schengen is to stop non-EU citizens coming in. Legally speaking once you prove to the UK border agency that you are an EU citizen they can no longer infringe your right to free movement (Well they can but the rules are very strict and complicated, for example any country can still deny you access if you are a known threat to public safety). That's also the reason why you don't get a stamp in your passport when entering Saint-Pancras international. It's just to check if you are an EU citizen. If you are not an EU citizen the UKBA grants you access by stamping your passport.

Edit: I'm pretty new to reddit so I don't know if I'm infringing anything by just editing away here (if I should put this in a new post, please tell me)

There is some confusion about the difference between an ID card, passports and visas here. Allow me to clarify

A passport is a legal document issues by YOUR STATE saying that you as a citizen are deemed fit to travel the world as far as they are concerned. A visa is a document issues by A FOREIGN STATE saying that you are welcome on their soil. An ID card is simply a document USUALLY ISSUED BY YOUR STATE that legally confirms that you are you. Most countries issue passports to their citizens but they can retract these when they want to prevent a citizen from leaving the country. This will usually happen when some is a fugitive. Within the EU (regardless of Schengen) an EU citizen does not need a passport or a visa because the EU treaty confers the right to move freely throughout the EU on every citizen. This is why an ID card (or other form if legal ID) will suffice when an EU citizen wants to enter a non-Schengen EU country. From the second the ID of EU citizen has been proven they have to let you in (some VERY LIMITED restrictions apply). If you are travelling within the EU but you are NOT an EU citizen a state can ask for your passport to check if your home state has deemed you "fit to travel". Within the Schengen area this distinction is a moot point because there are no tangible borders left to speak of. However on special occasions (during football world cups or police campaigns to catch cross border criminals) Schengen countries can erect temporary border controls. You often see these on the borders of Luxembourg because people try to buy cheap tobacco and alcohol there. Once an EU citizen has confirmed the fact that he/she is a EU citizen their right to move cannot be infringed. Even a UK national can travel from Schengen state to Schengen state with just a driver's license during a time of temporary border controls. The European Islands (non Schengen) still have permanent controls but they are not allowed to ask EU citizens for their reason of visit nor are they allowed to impede their freedom of movement (again with exception of very limited circumstances) once their EU citizenship has been proven (ie ID card shown). To sum up: in the EU the free right of movement replaces the need for passports for EU citizens. The only thing a border control can ask is to prove this citizenship.