At the heart of all the most successful 10:10 efforts, there's a secret weapon. But it's not a magic power-saving gadget or cutting-edge electric vehicle. It's the humble energy meter.

Over the last couple of years, we've seen countless examples of the power of good energy and emissions data to help an organisation make savings. Many of the biggest carbon cuts we've seen just wouldn't have been possible without good energy usage figures, but as with almost everything to do with climate change, carbon tracking and reporting is simpler, fairer and more effective when everyone's doing it.

That's why we're delighted at this week's announcement that from April 2013, carbon reporting will be made mandatory for the 1,600 or so companies listed on the London Stock Exchange.

Together with a few like-minded organisations, we ran a campaign pushing for this last summer, when the government launched a consultation on a range of options. 10:10 businesses united behind mandatory reporting for all large companies, and lots of them wrote powerful responses explaining the benefits of a single system that's clear and fair for everyone.

Then, when the government announced its 10:10-inspired 14% carbon cut, hundreds of individual 10:10ers stepped up, challenging ministers to match Whitehall's impressive savings with an equally ambitious reporting policy for businesses.

Then everything went quiet as the government machine rumbled away behind the scenes. Deadline after deadline slipped by with no announcement, and we started to fear a U-turn. But although this first phase of the new system includes fewer businesses than we'd have liked (we'll be pushing them to widen the net when the policy comes up for review in 2015), establishing the principle of mandatory reporting is a crucial first step, and a victory well worth waiting for.