Ferite bead on ignition wires?? does it work?

does this ferite bead attach to all ignition wires really work? whats the effect ?

 

Never seen it attached to HT leads like that before.
Here's some info from Wikipedia. Ferrite bead - Wikipedia Could it be a legal requirement in certain countries?

 

It has the almost magical quality of lightening your wallet and mysteriously transfers funds from your pocket to the pocket of the joker who thought it up.
You can buy ferrite beads by the bucketload from ebay Chinese suppliers for very little money.
Some ferrite beads, when applied judiciously, can actually do what's claimed for them *, but most are just panaceas.
In this case, the simple application of some decent resistor plug caps, plug leads or plugs themselves, would probably do the job just as well, if not better.

* For example, every LAN cable in my house is wrapped 6, 7, and 8 times (depending on size of ferrite) around a ferrite ring at each end of the cable before it plugs into its relevant PC, switch, etc. This has enormously reduced the amount of RFI I was getting from the LAN. Even at that, I was in no way going to spend the ludicrous sums asked for pukka ferrite rings from Amidon, etc, so I just used anonymous green Chinese ferrites, which work well for this application, and about a twentieth of the cost.