The London Mini A-Z is based on the world-famous book of the same name and offers detailed full-colour mapping of the central London area that is instantly recognisable to anyone who's ever used the paper A-Z.

The maps cover approximately 367 square kilometres of central London, more than 32,000 streets and include various places of interest such as train stations, hospitals and entertainment venues

The main advantage over the iPhone's built-in Google Maps application is that the Mini A-Z will work offline - there's no need for a phone or wi-fi signal to use the app.

Interactive functionality is limited, however. There are no route-planning facilities and when you zoom into the map the image becomes pixellated. You can find your current location on the map by navigating to the Options screen, however. And there is a very basic Search function (if a street name is abbreviated to 'Rd' or 'St' you have to enter the abbreviated version, for instance).

On the positive side, the A-Z app loads quickly, scrolls smoothly and looks good at the default zoom level. The instantly recognisable A-Z colour scheme looks great oon the iPhone's display and the street name's are generally readable.

The key question, though, is whether the app is worth the eye-wateringly high price of £5.99? Especially as you are only getting the mini version of the A-Z which goes only as far as Tooting in the south and Highgate in the North?

It's certainly useful to have the mini A-Z as a back-up to the Maps app but we'd like to see a cut in the price point or a decent functionality update before we can recommend this unreservedly.

To of the list of improvements would be a smarter search function, landscape mode and better image quality when the map is fully zoomed in. As it is though, the London Mini A-Z gives the impression of being rushed to market and ends up as OK rather than great. And at that price it needs to be great.