This is a pill that can prevent a pregnancy if taken within 3 days (72 hours) of having unprotected sex. The pill works better the earlier it is taken (or a coil can be fitted up to 5 days after to prevent a pregnancy).
Many pharmacies can provide free emergency hormonal contraception but not all pharmacists are trained to provide this service. It is a good idea to ring ahead and check that there is someone there who can help you.
You can also buy emergency contraception from pharmacies but it is expensive: about £26.
Emergency hormonal contraception works by stopping an egg from being released from the ovaries and making the womb an unpleasant place for a fertilised egg to attach.