Samsung might just have the mother of all phone leaks on its hands, with a video  appearing online of a supposed Samsung Galaxy S4 being put through its paces. 

The phone, which appears to be fairly thick and hefty as well as a touch laggy, has us wondering if it is a development device or the build journalists will be shown at the 14 March launch in New York.

The front of the handset is black, with the other side set in a gloss white - which does appear to agree with the black and white posters currently sitting in Times Square. It also has the same faux brushed-aluminium look as the previous Galaxy S3, and is obviously the same lightweight plastic.

The metallic wraparound seen in Samsung's own Twitter pic this morning is also present on the handset. On top of this, the leaked video clearly shows the Galaxy S4 packing quite a screen, with rumours suggesting a 4.99-inch 1920 x 1080 pixel display to compete with the likes of the Sony Xperia Z and HTC One.

We are fairly impressed by the video, which does appear to be showing an as yet unseen handset from Samsung. That thickness is what has us apprehensive though, so don't take it as concrete evidence of what the new phone will look like.

On the back of the handset appears to be a dual-SIM slot, so this looks to be a variant that will probably have limited global distribution, as well as a microSD option to keep memory fans handy.

The hands-on video also gives the camera a brief whirl which shows some sort of burst mode and new look UI.

Listed as the GT-i9502, the Samsung leak could very well be the new SGS4. It runs on Android 4.2.1, has a massive screen and an AnTuTu benchmark of 26118. There is also mention of a 1080p screen as well as a quad-core ARMv7 processor.

Whatever happens, all will be revealed on 14 March. Pocket-lint will naturally be bringing you coverage straight from the event.