Re: Elphin safety
[A]nd an anecdote from some touring entertainer long, long ago concerned a troublesome lavatory cistern whose owner explained to her theatrical paying guest, "You have to surprise it, Mr. ____" - which I suppose means a sudden sharp pull.An old cast-iron Burlington, by any chance? https://www.practicaldiy.com/plumbing/cistern_burlington/cisterns_burlington.php These are inherently fussy about timing, less so if the float valve is adjusted to set the water level with millimetre precision.
Alternatively, it could have had the beginnings of a split in the syphon diaphragm: https://www.practicaldiy.com/plumbing/cistern_syphon/cisterns_syphon.php This usually causes temperamental flushing at first -- the cistern will flush successfully if you can work the handle quickly enough to get enough water over the weir of the syphon before it drains away via the split -- gradually becoming impossible as the damage gets too severe. You can cut a replacement from a heavy-duty polythene sack with a sharp knife.
Mine's the one with the adjustable spanner in the pocket.