In BS 1363-compliant sockets, the live and neutral openings (the socket is polarised) are protected by a shutter (clause 13.7.2 of BS 1363-2 requires that Europlugs will not open the shutters.(Wikipedia)) which only moves out of the way if the earth opening has a shaped pin inserted (There are other mechanisms). If you do that you can force a Europlug into the live and neutral as Europlug pins are flexible: the nominal dimensions are that the BS1363 Live and Neutral pins are 18.2 mm apart (22.2 mm between the centres) whereas the pins on a Europlug are nominally 13.5 mm apart (17.5 between the centres), but Europlug pins are not parallel - they are flexible, and are 13.8 mm apart at the base (18.6 mm between the centres - the pins are narrower at the base). However, if you try too hard, you are likely to break a pin.
The device in the picture doesn't look like a standard Europlug, as the pins are not insulated.