A slang term used in Australia and northern England to describe something or someone which is exceptionally good or attractive. Of late the term has seen a slight revival across the UK due to its use as one of David Dickinson's catchphrases on the students' favourite TV show Bargain Hunt. His recent autobiography is titled "The Duke: What A Bobby Dazzler". In Australia there is apparently an equivalent term ruby dazzler although I'm not sure which is more commonly used. In everyday northern English usage, it's pretty much synonymous with belter, i.e. it's used most often by working class folk over 50. An exaggerated example of usage:
"Eee our Dave, is that yer new car? It's a rahht bobby dazzler!"


One explanation for the origin of the term is given in 'A Dictionary of Slang and Unconventional English' by Eric Partridge:

In the heyday of Cycling Clubs the police would lie in wait for their dusk return. Those without lights got in the middle, those with the new fangled very bright acetylene lamps rode on the outside, their lamps were the Bobby Dazzlers.
(in case you aren't aware, bobby is a slang term in the UK for a policeman.)

To be honest that sounds a little far fetched to me, and the entry is marked se non è vero, è bene trovato so draw your own conclusions.

The term was featured by Australia's ABC Classic FM on its Word of the Day slot with a somewhat more credible explanation.. bobby derived from "bobbish", an 18th century word for healthy or spritely and dazzler coming from the idea of someone being dazzlingly beautiful.

Sources and further information
ABC Classic FM - http://www.abc.net.au/classic/breakfast/stories/s557696.htm
The Duke's book - http://www.amazon.co.uk/exec/obidos/ASIN/0563487240/ref%3Ded_soc__3_2/026-8542359-9962828