It's the new thing phone makers do. Release a massive important flagship model to huge fanfare, then, a few months later, pretend it's too big and launch a smaller mini variant for those after something not so huge. The key thing here is Sony's not scrimped on the internals for this shrunken model. The Z1 Compact really is a big phone in a small case.
A phone that doesn't look anything like the Xperia Z1, but offers a 720p resolution display backed by a high-end Snapdragon 800 processor and 2GB of RAM to make it very nearly equally as powerful as the popular Z1. And the same 20.7-Megapixel camera as its big brother, too.
People who claim they don't like today's trend for huge phones. People who want to be able to comfortably use a phone in one hand. People with small hands. People with small pockets.
It's a rectangle. The glass back means there's no curvature here, so it somehow manages to feel pretty chunky despite only measuring 9.5mm thick. The edges have been smoothed down a little so it's not overly angular and feels soft in the hand, plus the power button's well placed for thumbing at just above the middle of the right-hand edge.
Waterproof boasts mean the USB, microSD and microSIM connectors are hidden behind robust stoppers, which further smooths the sides but will have people sighing into their pillows at annoyance at the PAIN and MISERY that is having to open a stopper to plug the thing in to charge.
The loud and bass-heavy speaker is positioned along the bottom of the Z1 Compact, with Sony's software buttons beneath the display. It's not a great phone to own in winter, as the combination of glass and metal makes it cold to the touch and chills our poor, battered fingers.
With a display of just 4.3-inches, it's surprisingly easy to use the Z1 Compact in one hand. You can reach the notifications bar without contorting your grip, while menu buttons in the top-left corner of apps are also reachable. After years of being exposed to bigger and bigger mobile displays, it's nice having something you can casually flick about in one hand.
Sony's Android customisations are incredibly thorough. Most of them are improvements or at least offer something not present in stock Android models, with everything from a white balance adjustment for the display to a wide range of power-saving modes in here to give users some extra stuff to fiddle with.
The camera is a key reason to consider the Z1 Compact. The 20.7-Megapixel output is great, with realistic colours, plenty of detail and a flash that doesn't nuke things and human faces at close range.
And the camera software is absolutely heaving with options, some useful some a bit bizarre. The burst mode is extremely handy, the augmented reality dinosaur overlays and Sony's built-in backup support with its PlayMemories cloud server not quite so essential.
It's also very fast. We've been using the Moto G for a month or two, and had convinced ourselves that was as fast as Android phones could be. It's not. The Z1 Compact is fast fast, seamlessly blazing around its Home screens and apps. Sony really has stuffed high-end monster-phone performance into this chunky little chassis.
Sony's filled this with way too many of its own apps. Most want to sell you something or have you subscribe to a thing, and it all feels so... messy. You're redirected to numerous web portals to sign in to Sony services, grant approvals, download more apps and agree to agreements, plus there's masses of pointless duplication. Most download links within the Sony Select app store link to Google Play. So why does it exist? Well, we know why -- marketing and sales and money -- but for actual users it's a waste of time.
The oddest of Sony's many, many OS customisations is its Info-Eye augmented reality, location-based search app thing. The idea is you take a photo of a thing, Sony scans it and your phone pings back data about what you just took a shot of.
Only it hardly ever worked with anything we tried, and we can't think of any real-world scenarios in which we'd want to take photo of the Eiffel Tower and have our phone tell us we're looking at and near the Eiffel Tower, or to scan a barcode of a book to have a phone say what the book is called. Weird thing.
-- Battery life is great. The Z1 Compact is a member of the two-day club, if you treat it carefully. That's one of the biggest reasons to upgrade/downgrade/sidegrade yourself to a smartphone with a smaller display. It's like living in the late 1990s again.
-- The camera really is the making of it. It's so fast and with a nice two-stage shutter key to force it to focus. Not that you need to, as the auto-focus itself is quick and reliable.
-- Sony's media apps are super stylish. The Walkman player is lovely to look at if you can ignore the way Sony's using it to push its own Music Unlimited service, as is the Movies player with animated top bar. Even the Gallery with pinch-zooming, resizing image previews, is fun to fiddle with and very pretty.
-- Another nice touch is a "gloves mode" that enhances screen sensitivity. It means you get big circles popping up over the display as you aim your pokes, but it does indeed let you control the Z1 Compact with fabric-covered fingers.
-- There are too many pre-loaded apps you can't remove, though. Sony's Reader and Socialife news feed aggregator, PlayStation Mobile, Smart Select, Sony Select... the app drawer is heaving with things many users won't want or need.
-- The 720p display's perfect. There's no loss of quality in the drop down from 1080p when compared with the larger Z1, as on this modest 4.3-inch screen you'd need to be examining it under a microscope to notice any loss of pixels. It's bright, great for media, and Sony's fonts appear sharp and clean.
Well now, that depends upon how much you hate big screens. If Sony can sell a phone to everyone who's said they want maximum power in a smaller chassis, then yes, we can imagine lots of people buying and loving the Z1 Compact.
Thing is, with an RRP of over £400, potential buyers face a tough psychological battle over making the decision. You're paying the same amount of money as a big thing, but getting a smaller thing in return. That's a hard decision for even the most rational of consumers to take.
We know what the first 30 comments are going to say. The Moto G is only £100 and offers a similarly modest screen size, so why buy this for £400? Well, because the Moto G has an abysmal camera that knocks mobile imaging quality back about five years and puts you off the idea of taking photos altogether, whereas the Z1 Compact is an immensely powerful snapper. That's why.
It's also a lightning fast phone with a beautiful display, but it's not as sexy a piece of kit to hold and be associated with as the rightful owner as the full-size Z1.
We like using it, though. It's fast and we approve of most of Sony's deep Android customisations, without ever feeling hugely exciting. But the Z1 Compact does fill a very important gap in the market. For that it deserves your consideration if you want cutting-edge power inside a modest case.
Price: £449; soon to be available on networks
Processor: Quad-core 2.2GHz Qualcomm MSM8974 Snapdragon 800
Screen: 4.3-inch 720 x 1280
Memory: 2GB RAM
Storage: 16GB, micro-SD
Camera: 20.7MP rear camera, 1080p front camera
OS: Android 4.3 with Sony UI skin