Is this the Surface Phone? Microsoft teases mystery folding smartphone on Twitter

For fans of Microsoft's hardware, the fabled Surface Phone is the Holy Grail. Shrouded in rumour, wild speculation and vague teases, Microsoft's inevitable return to the smartphone sector after its Lumia series bombed in such a spectacular fashion remains an intriguing prospect.

With even minor glimpses of a phone near a Microsoft device setting Redmond enthusiasts' alarm bells ringing, it's unsurprising that the appearance of a mysterious smartphone in a tweet from Microsoft's cloud computing-focused Azure account has sent the rumour mill into overdrive.

In what was otherwise an innocuous tweet (below) advertising a virtual developer class teaching Javascript, the post included an image containing details for the free lesson and a picture of a pair of hands holding a large-screened smartphone that doesn't fit with any Microsoft product currently on the market.

If - and that's a rather large if - this is the elusive Surface Phone, then it could be something quite unlike anything we've seen before.

The pictured, phablet-like device has an edge-to-edge display much like the Samsung Galaxy S8, the LG G6, or even the upcoming Essential Phone. However, the real point of interest is what's tucked away behind the phone.

It's a little tough to make out exactly, but it vaguely looks like the handset has two side-mounted flaps that have been folded to the back - an observation that's even more interesting when you consider that Microsoft has patents in place for foldable display technology.

The problem? For a start this is probably an image plucked from a stock archive. There's also the small matter of the copious amounts of Photoshop work that is visible upon close inspection, not to mention the fact that it's still live on social media.

Microsoft's smartphone comeback will no doubt be an event with a little more fanfare, and it wouldn't want a mundane tweet from its Azure wing to spoil the festivities. Sorry Surface fans. The wait continues.