A three legged race? Yes, for most users in the UK and China, since Cortana is no use without Windows Phone 8.1 - so both are needed for the voice functionality, already active for many USA users, to work. Cyan is rolling out already (albeit slowly), while a new posting in China from a media outlet invited to a 'Cortana' event on July 30th leads us to suspect that next Wednesday is indeed the date Cortana may hit China officially. And, along with other clues around the Interwebs, with 'China and the UK' being included at every stage in Microsoft missives on Cortana, there's every chance the UK will also get the functionality on the same day.

From the ZOL posting (here machine translated):

Microsoft Cortana voice assistant when they could arrive in China? I believe that many Windows Phone users have been waiting for a long time. Well, now we seem to have been answered. Currently ZOL mobile phone division has received an invitation to Microsoft aspect display Cortana will be July 30th official visit to China. The invitation caught in a brown envelope like exquisite packaging them, which is an imitation of the Windows Phone handset shape cardboard card, which will be marked with Microsoft at 14:00 on July 30 to 4:00 in Beijing Conrad. 

But the main interface which Cortana is the Chinese version of Windows Phone8.1 systems do not have, so it is easy to think that this conference may not be the protagonist of the new machine, but Cortana. Invitation inner information more people confirm this - an obvious Cortana blue LOGO: "China, here I come."

Interestingly, the post also goes on to say that Cortana might be renamed for China, perhaps as 'Huna'.

It's interesting to speculate what form Cortana will take when first introduced to UK users (perhaps) next Wednesday. Assuming that the users in turn have had Windows Phone 8.1 sent out to their devices by then. My references to a 'race' are because it's by no means certain that 8.1 will be in place for most devices. 

Hooks for Cortana is built into all 8.1 installations but not turned on by default. Activation is server-side, so most Lumia 625 and 925 users (who already have 8.1 as an update), plus existing Lumia 630 and 930 owners*, will simply see Cortana pop up (or perhaps a prompt to install a particular module) when they use their search control. And I wouldn't rule out a helpful 'It's here!' message sent out to their registered Microsoft account email addresses.

For the rest of us, even if Cortana is switched on, we'll have to wait untl 8.1 appears (in the form of Lumia Cyan) as an update before we can start asking Cortana to perform animal impressions and tell jokes....!

* Plus those on the Developer Preview programme - probably!