The handyman unscrewed the u-bend to inspect it for any sign of a blockage. He found that the whole u-bend and waste pipe were completely blocked with what seemed to be cement. After a quick call to one of the senior handymen the cause of the blockage became clear.
The cement like substance was actually limescale which had been encouraged to grow so aggressively due to the constant presence of uric salts and bacteria found in urine. The tenant had obviously been using the basin as a urinal for some time which had resulted in the u-bend and waste pipe becoming the ideal environment for limescale to build up quickly until the basin waste pipe was solidly blocked.
Once we knew that the problem was limescale we were able to treat it with an acidic solution known as 'Spirit of Salts' which over time will dissolve the limescale. Using this acidic solution combined with 60 minutes of traditional roding we were able to clear the blocked waste pipe. We fitted a new u-bend and instructed the tenant that he should not pee in the sink.
A strange job, but an interesting one among handymen and plumbers who deal with blockages.