Just as in the US, Prime Same Day can deliver a parcel to the recipient within six to 10& hours, meaning that anything ordered before 12pm will be delivered that evening.
Prime Same Day shipping isn't quite as radical as Prime Now, the £6.99 ($10) option to get packages within an hour, but it's included in all Prime subscriptions for free.
According to Amazon, the new service is available to anyone in Greater London and a few of the surrounding areas, such as Hertfordshire and Berkshire.
Amazon has competition in the same-day delivery space. Argos, one of the UK's largest retailers, also recently announced UK-wide same-day shipping.
Disclosure: Jeff Bezos is an investor in Business Insider through hispersonal investment company Bezos Expeditions.