michael newport wrote

A couple (late 20's) who live in an adjacent St have a Husky dog.
It seems uncontrollable and vicious. It's always on a lead which
is good except the woman is clearly at the limit of what she can
manage to do to hold it back every time they pass someone.
Am pretty sure it would attack, should it slip the lead.

Unlikely IMO.

The Bloke is struggling with it too but it seems to listen more to him.

I like dogs very much and have had Alsatians and Labradors
in the past so know a little of their nature. But the husky to
me seems more of a pack-animal than most domestic dogs.

But they don't attack people much.

My concern is that there are quite a few young children in
the area and feel the need to have the owners (who seem ok)
to realise the risk. I don't think "having a word" will work

Problem for them is that there isnt anything much they
can do except never walk the dog again or get rid of it
and it is very unlikely that you will be able to convince
them to do either unless they are on the verge of doing
that already, in which case you don't need to do anything.

and probably escalate things.

Not necessarily, but could well agitate the dog.

Only a week ago it pulled the lead out of Mrs' hand and had a
go at attacking a car (my wife was driving it so saw it happen).
Stopped in the middle of the road while this dog circling the car!

Sure, but it clearly didn't actually attack it.

Any suggestions what to do for best?

Not clear that there is anything.

RSPCA do anything?

Unlikely unless you manage to fluke someone prepared
to approach them who is a hell of a lot better than average
at encouraging them to get rid of the dog which is unlikely.

The Cops?

Nothing they can do until something does happen.

Council?

Ditto.