We've always been advocates of the Sony RX100. Both the original and Mk II models offered exceptional image quality in a truly pocketable design that, to some degree, rewrote the expectation of what a compact camera could do. The Sony Cyber-Shot RX100 III goes one step further by upping the feature set so considerably that few competitors offer anything even close.

The RX100 M3 retains the same 20.1-megapixel 1-inch back-illuminated sensor, but the lens sees a huge change: its now a 24-70mm f/1.8-2.8 equivalent. That means a wider-angle offering and a brighter aperture range than in its sister models. It does mean the top-end of the zoom isn't as significant as the 100mm the series had delivered until now, though, as Sony has focused on maintaining the camera's small scale rather than bulking the RX100 MkIII out too much for the sake of focal length.

Despite only being a few millimetres fatter than the MkII model - the RX100 III is 41mm wide rather than 38mm - it also contains a built-in OLED electronic viewfinder. And by contain we mean quite literally: it's tucked away inside the body, only to be revealed by tugging on a small switch to the side of the body. The finder pops up, the rear eyepiece then needs to be pulled outward to complete the setup.

READ: Sony Cyber-shot RX100 MkII review

This two-part finder "construction" did worry us that it might be a little fiddly and wobbly, but it's not at all. It's easy to set-up and solid once in position. A simple push down back into the body and it's tucked away out of sight. Although at the moment stowing the finder switches the camera off which is an annoyance, but one that Sony representatives told us they were looking into.

Those who happen to wear glasses will know too well that small viewfinders are often less than useful, but in the RX100 III that's not the case; the OLED panel delivers a 1,440k-dot resolution and the 0.39-inch size is ample. Looking at the small body and it's a minor miracle that it's been designed to be hidden away in the design. We're big fans of what Sony has done here.

On the rear the 3-inch, 1,229k-dot WRGB LCD screen is now mounted on a 180-degree tilt-angle bracket. That's right: Sony has got in on the selfie craze by enabling the screen to tilt all the way up into a vertical position. Whether you'll use that often or not, the ability to easily pull the screen away from the body for waist-level work is great and the addition of a white pixel layer makes for a bright display.

In use the RX100's smooth-rotating front lens ring is a highlight for adjusting manual focus. Or set it to control one of the many settings as you wish: we set it to adjust aperture in aperture priority mode, and despite not clicking through f-stops upon rotation (like the Olympus Stylus 1 can) there is a subtle digital "click" sound emitted.

Flick the mode dial into a new mode, such as shutter priority, and it's possible to customise the ring to adjust a different setting. We like the detail of each mode offering separate customisation, while a custom "C" button on the rear means quick access to additional settings.

READ: Olympus Stylus 1 review

Autofocus is also very fast. We were shooting in a dark room, where even under studio lights diffused by softboxes the Nikon D610 we were using for product shots was opting to shoot at ISO 1600 at f/4.0. Picking up the RX100 III and turning it around to face the areas of the room not lit by the lights and autofocus still snapped subjects into focus near instantly. We didn't get to use the camera in better light, but can only presume it will be even stronger in such conditions.

The available autofocus settings have also been tweaked. The single focus area can be toggled between large, medium and small sizes for more control and accuracy. Still no "pinpoint" mode like the Panasonic G-series, but it's a step in the right direction. If close-up shooting is your thing then the new lens is more capable in this department too: 5cm focus is possible at the 24mm equivalent, increasing to 30cm at the 70mm end of the zoom.

Sony has still refrained from adding a touchscreen into the RX100 mix for the third-generation model. However, we can understand why: there's so little bezel on the screen that accidental presses of the screen when tilting it would likely happen a great deal. On the other hand we think it should be included as an option for quick press-to-focus control.

Movie mode also sees a bump thanks to XAVC S 50Mbps 1080p and 120/100fps 720p capture, including a mini HDMI clear output should you want to use a larger scale screen for preview. That doesn't mean "clean HDMI out", though, as it's not possible to send an uncompressed signal to an external recorder like you can with some other Sony kit.

Elsewhere there's a built-in Neutral Density filter, Wi-Fi for image sharing and remote control, a variety of picture effects and ISO sensitivity now tops out at 25,600 thanks to the latest Bionz X processor. We've not been able to test these features specifically in our short time with the RX100 MkIII thus far, nor how well the battery life will last or the latest processor will render image quality - but that's all to look forward to in our final review as and when we have the camera.

The main crucial thing we don't yet know is a price point or release date. Our logic is this: the RX100 M3 will hit the shops in June, two years after the original RX100, and is likely to be priced around £200 more than the RX100 II on account of the built-in viewfinder. So the tune of £799 sounds about right to us. And before you choke on your tea at the prospect of so much cash for such a small camera, think how the Sony stacks up against the comparatively gargantuan Canon G1 X MkII.

READ: Canon PowerShot G1 X Mark II review

We think Sony is on to a real winner with the Cyber-shot RX100 III, albeit one that you'll need to save up for. But if there's a camera that could be tipped to be king of the compacts then this is it. There might be larger sensor offerings out there, but none are as small and truly pocketable as the Sony.