I visited a McDonald's test kitchen to try its biggest menu overhaul in a decade. The burger patties are a big improvement, but the new Big Mac is too sweet.

• McDonald's is rolling out a new burger bun recipe in the US, UK, and Australia.
• It's also changing the way it cooks burger patties and stores some of its fresh ingredients.
• The new bread is good, but the new Big Mac tasted too sweet.

McDonald's burgers are getting a new look. The menu shakeup comes as the fast food chain prepares to celebrate its 50th anniversary, and constitutes the biggest change the chain has made to its food in 10 years.

I visited the McDonald's UK head office in East Finchley, London, to hear more about the changes, and to get a side-by-side comparison of the old and new burgers.