You might not have known already, but Amazon Prime members in certain cities have the option to order deliveries to arrive on the same day. Indeed, they can even arrive within one or two hours, with the latter available as a free option.

Known as Amazon Prime Now, the service offers thousands of products for speedy delivery and bar the delivery cost for one-hour turnaround, it is free for Amazon Prime customers.

Prime members have to live (or work) in "selected postcodes" but that's the only main caveat.

So here is a list of the locations Amazon Prime Now covers and explanations of how you can use it...

Amazon launched its one-hour delivery service in the UK in the summer of 2015, starting in the capital London. It had already been successfully received in the US, being first available in New York at the end of 2014.

It enables Amazon Prime subscribers to order items through a dedicated smartphone application or browser at primenow.amazon.co.uk and have them delivered on the same day, with one-hour deliveries costing a premium, but two-hour delivery windows being free.

It doesn't cover every item on Amazon.co.uk, but there are more than 15,000 products available, including groceries. Whether something you require is available to order through Amazon Prime Now depends on your location - as it needs to be within a short ride for the courier.

The dedicated app and browser location determine which items are available to you and filters out the rest, so you should never see an item come up that you cannot order through Amazon Prime Now.

To begin with, you need to have Amazon Prime membership to use the service. That costs £79 a year but also includes complete access to the vast amount of free content on the Amazon Instant Video streaming platform, access to Amazon Music, the company's fledgling rival to Spotify, free next-day postage on a huge amount of the online retailer's stock, the Kindle owners Lending Library and several other incentives.

Amazon Prime Now itself costs £6.99 for each delivery if you want your items delivered within an hour of ordering. It is completely free if you are willing to wait a little longer though; it offers free two-hour slots throughout the day, between 8am and midnight.

Items, on the whole, are the equivalent price to their listings on Amazon.co.uk.

Orders must be, at minimum, £20 in value, but that can include many items.

If you've never used it before, you can get £10 off your first order, as long as it is worth £40 or more. Just type 10NOW40 into a box at checkout.

Amazon Prime Now is available through a dedicated application for iOS, Android or Fire devices. Check here for download locations.

It is also available in-browser at primenow.amazon.co.uk.

When you first log in, you determine your delivery postcode, which you can also change at any time in case you want to have an item delivered to you at work, for example.

You use the app or site much like general Amazon applications, by placing items into the basket.

When you check out though you will be presented with the different options for delivery. We've found it offers a couple of different two-hour time slots for free delivery as default, or you can opt to pay for one-hour delivery by selecting that option in a drop-down menu.

Once you have checked out, you can track the progress much like on the main Amazon site, although this time, as soon as the courier has departed you can track them on a live map within the app itself.

Many of the main cities in the UK are covered by Amazon Prime: Birmingham, Glasgow, Leeds, Liverpool, London, Manchester, Newcastle, Portsmouth and Sheffield.

Amazon Prime Now is also available in some regions of Surrey, Hampshire, Berkshire, West Yorkshire and South Yorkshire. These include Camberley, Lightwater, Aldershot, Bradford, Wakefield and Huddersfield.

Glasgow regions covered include Parkhead, Shawlands and Paisley, as well as surrounding areas, such as Motherwell, Kilmarnock and Cumbernauld.

You can find out whether you can get Amazon Prime Now deliveries in your home or work place by entering your postcode into Amazon's postcode checker here. If it is okay, you should download the app to your phone or device and get ordering now.