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I find the idea that an appliance could "blow up" on a UK power supply if you reverse the "live" (phase) & neutral in the plug top a little over dramatic!
During the course of my work I have encountered plugs with reverse polarity on many occasions, & all the appliances work normally. This does not mean to say they are safe, as any single pole control devices; switches, thermostats etc. would be in the neutral conductor. This could be a shock hazard, if for example you were changing a bulb & accidentally touched the pins, thinking it was safe with the switch off.
British regs. prohibit a single pole switch in the neutral, if the neutral is switched all associated phases must be switched simultaneously.

The purpose of the fuse in a 13A BS1363 plug is to protect the appliance cord only from short circuit. If the appliance requires additional protection it has to built in to the appliance, I believe this is an IEC standard.

Reverse polarity in the actual fixed installation wiring could be very dangerous, depending where it occurs.
The worst case would be TNC-S (PME) reversed
on the incoming supply before the cut-out (I know of this happening). All bonded metalwork would be live at 240V, along with every earthed point & appliance in the installation.
This is the 1 downside to TNC-S earthing system.

These are just a couple of reasons that us Brits are obsessed with maintaining polarity throughout our "eccentric" electrical installations.

As other members have stated the neutral is always permanently & solidly earthed in UK public supply systems.
Most systems are TNC-S or TN-S, with TT systems only used for rural supplies (though TNC-S is the norm in my area), building sites & petrol service stations (TNC-S not permitted) or any other location where PME (TNC-S) system is not allowed.

About appliances "blowing up". Well, I must have gotten it wrong. (misinformation)

The only thing that still bothers me is: why in a british PLUG (not in the socket) do you HAVE to put the brown to the Live (which is fused) and the blue to the Neutral. It would be as safe the other way round.

[This message has been edited by Belgian (edited 10-20-2002).]

Belgian,
I agree that in many cases reversing the brown and blue at the plug would have little or no effect on safety. You see the stickers attached to British cords about how essential it is that the wires are correctly connected though.

Many of the appliances sold in the U.K. these days are sold as the same model right across Europe. The two-prong "Euro" plug is non-polarized, as is the widely used Schuko plug (and a few others, e.g. in Italy). Even in France where grounding plugs are polarized, nobody seems too bothered about which way phase & neutral are connected at sockets.

The IEE is always quite adamant that all single-pole switches, even those inside equipment, should be in the "correct" side of the circuit.

There would be a case for some old electric heaters where the element terminations can be touched through the grill. If the switch were in the neutral, then somebody could touch an energized terminal believing the heater to be safe. But they don't allow those to be manfactured these days anyway.

The only other case I can think of is where a primary fuse is included on the supply input (typical of some radios, TVs etc.) and reversal could remove the protection by having that fuse end up in the neutral. It would still provide overcurrent protection, but not protect against ground faults.

Perhaps with the prevelance of TN-S and TN-C-S systems in Britain this was a major concern, whereas so much of residential service in Europe is TT where the main GFI/RCD would provide ground-fault protection. (As would also apply increasingly in this country.)