Squeaky neutral?

[Parsnip]

Have noticed that the car has developed a bit of a high pitch squeal when revving it in neutral - discovered due to the battery being a bit flat and having to jam the loud pedal down to get the engine to catch (I am not a chav who sits bouncing it off the limiter while stationary, honest!) - seems to just be when in neutral and you give the throttle a decent stab - doesn't do it with small blips coming down the gears and never does it under load.

Any suggestions? Not even had a look under the bonnet yet to see if its anything obvious, although I can't think what it would be - loose belt somewhere maybe?

[alex290568]

Loose alternator belt?
Would also explain the flat battery