Booby on the beat?

Dear Alan:

Would you please be so kind as to explain the words, phrases and expressions that I’ve put in bold? As always, thank you very much for your kind help.

Bobby on the beat? A sure-fire way to see crime double, idyllic village finds

This is the place where the crime rate almost doubled last year - in spite of an experiment to pay the local police force to return a bobby to the beat.

It seems an unlikely place to have holed below the water all those political shibboleths about how Britain would return to some Dixon of Dock Green idyll if only we could get more policemen out on patrol.

Thanks again for the help.

Paolo

On the beat – on patrol out in the streets
Sure-fire way – 100% sure

‘It seems an unlikely place to have holed below the water all those political shibboleths’ =

‘to have undermined all those old fashioned political principles…’

DIXON OF DOCK GREEN -
was a popular tv series in the 1950’s and George Dixon was the kindly old style police officer who was loved by everybody - very nostalgic etc. in fact the series developed out of a film called ‘Blue Lamp’, which was very successful at around the same time and starred the film actor (probably his first film?) Dirk Bogarde, who incidentally played the lead in the film based on Thomas Mann’s ‘Tod in Venedig’. This is all very interesting but I wouldn’t dream of using material like this in any language lesson.