Cistern not filling

[Proofraider]

For some reason this morning the cistern on the bathroom loo isn't filling up after flushing - I can hear the water drawing from somewhere and that just goes on and on but the loo isn't filling and there's a thin trickle of water coming down into the bowl. Before I start hunting for a plumber, any suggestions please?? Thanks!

[carrust]

Have you tried jiggling the ballcock? It could be jammed.

[terence7556]

the valve that controls water in and the ballcock rises to shut off the water is gunged up or shot, possibly the washers, although that usually does,nt allow the water to fully stop
are all the other loos filling as normal? if so change the inlet valve

[Proofraider]

Thanks, folks - managed to sort it by filling the cistern with a bowl of water then flushing and it righted itself, but it's still a bit iffy so have got someone sending me a quote for replacement. He said it's a common problem in our area which has really hard water and as fittings get old they get worn and clogged. Will know what to try next time!