The Oyster system has made a big difference to London’s underground tube system.

An Oyster card allows you to use most of London’s public transport network (though a few stations remain outside the system).

It lets you bag discounts on the standard fare as well as allowing you to avoid the inconvenience of queueing for tickets.

The system automatically saves you money by calculating the lowest fare at the end of each day based on your exact travel that day.

If you travel more than planned, it automatically bills you the cheapest sum instead of expensive single tickets.

So does the Oyster scheme have any downside?

It can feel a bit complex to start with, as you need to buy an Oyster card which costs a small deposit. You should however make this back in money saved very fast.

You also need to “touch in and out” on all parts of your journey. But you’ll pick this up quickly if you copy the many Londoners heading to and from work.

So unless your trip to London is a very brief trip, you’re certainly advised to get onto the Oyster scheme. As far as I know, Oyster cards have no expiry date: you should be able to use them when you return to London.

If you don’t expect to return to London shortly, you can normally get your deposit back (but do check the process at the London Underground ticket kiosk before you buy).

There’s also a so-called “Visitor Oyster” available from selected outlets which is supposed to be designed for tourists. But it is not clear at the moment if this has any special benefits.

If you absolutely don’t wish to deal with an Oyster card, please ensure that you always buy the cheapest London travelcard for unlimited travel for the day on both the tube and buses. But you should wait until after 9.30am on a weekday since it will then cost much less.

You can also get a weekly travelcard for a greater discount if you’re staying longer, but this does require you to provide a photo.

Remember: Oyster cards and travelcards can be used on both the tube and bus system, though not at all national rail stations. Do check before you travel.

For more information about Oyster and public transport in London, do visit the official Transport for London website.

Finally, always wait until later than 9.30am on a weekday to avoid paying London’s super-expensive peak fares.

The author shares inside tips on the best of London in addition to real-time London hotel tips on Twitter.