Known extra units put on at last minute , several times at several different locations , and FCC have run an extra service due to severe crowding on the last booked train to their utter credit. (empties from Cricklewood to form an additional to Bedford from St Pancras ....)
My best one , is when back in the day , Leicester I think played West Ham and the game overan so these Midlanders turned up at St Pancras with no train till the next day. So the BTP chaperoned these fans to Euston and demanded a special to Leicester from there.
I know their railway geography can at times , be less than perfect but it took a lot of persuasion that a 321 could not get there. After a lot of "firm conversations" I reluctantly offered an 8 x 321 to Rugby - non stop -as the best we could do. Rugby Night supervisor advised later a huge collection of Police transits attended and took these fans on by road to Leicester. They were incredibly well behaved apparently.
One of my drivers ran an extra on the Watford to St Albans one night without telling anyone - (he was putting the train away and a couple of customers turned up) - well the box spotted it of course , (it only ran to Garston) - the driver , who you could not fault him for his customer service ethos was reminded of the need to communicate and we left it at that.