Pizza Express unveiled its new app today, whetting users' appetite with the promise of a totally free pizza. But unfortunately the launch has proved sloppier than a Sloppy Giuseppe, with disappointed customers left sitting in restaurants unable to get the deal.

We featured the deal earlier today and it's been widely covered on deals sites and by the national press, prompting a huge number of customers to try and save some serious dough.

But unfortunately many have been unable to get a slice of the action - because they've found the app has repeatedly failed to load or returned error messages when they've tried to use it.

What is the ‘free pizza’ deal?

If you download and fully register your details on the new Pizza Express app, you’re supposed to be sent a code within the app within six to 12 hours.

This code will get you your choice of either one free 'Classic' or 'Leggera' pizza, a salad or an 'Al Forno' dish (normally £9-£12ish) any time on Sundays to Thursdays, with no requirement to purchase anything. See full details in our Pizza Express free pizza deals write-up.

What’s gone wrong?

Sadly the app simply hasn't been working for many for a number of hours, with many disappointed pizza-lovers taking to social media to complain.

Some diners who've gone to a Pizza Express restaurant expecting to use the app have been left with a bad taste, after finding they've had to pay an unexpected bill because they couldn't access the app to show their offer code.

App not working? There’s still plenty of time to get the deal

Pizza Express told us ahead of the launch that the offer is expected to run for at least a couple of months and if you get a free pizza code, it will be valid for six weeks.

So there should still be plenty of time to grab this deal once the frustrating technical glitches have been fixed – though of course, there is always a chance Pizza Express could pull the offer early if it becomes too popular.

What does Pizza Express say?

A spokesperson said: "We're delighted there's such high demand for our delicious pizzas and our fantastic new app, and we’re sorry there's been some technical issues today.

"We're working hard to get things up and running quickly and as there's no hurry - free pizza can be claimed up to six weeks after the app is downloaded and the user's profile is completed - we'd recommend waiting a couple of days before downloading the app."