I remember when they dug up st andrews street (i think thats the name, the bit outside lloyds bank and boots)... had just finished putting it back together again, put all the paving back, and bing, a few months later it was all dug up again. Apparently the services - gas/water etc can't coordinate themselves to do jobs on the same tunnel at the same time, so they dig up the same bits separately instead.
bloody stupid...

as are things like this:
http://www.livejournal.com/users/casby/24537.html