Not nonsense at all.... I did jury duty in january last year where a judge in manchester crown court pretty much summed up as much in a case i sat on. Of course you know more than he does i am quite sure
In writing or email... ? i suspect the latter in which case.... again not admissible. A hand written letter from the suspect can be used as evidence but again its circumstantial as the letter cannot be proved 100% to have been written by the accused. An expert can pass an opinion of how likely it was to be them but it is not always so clean cut. ( again the case i sat on involved emails.. letters... txt messages and recorded phone calls, most of which were not allowed by the judge. )
I had always assumed that txt messages were an ok form of proof but the judge would not allow them because it cannot be determined that the accused was the one sending and receiving the messages, only that their phone was used... or their SIM card was used. Most of the case hinged around the use of email and txt messages and a lot of the evidence was simply disallowed by the judge. The same went for emails... the only thing you can prove is that they originated on the computer owned by the accused, NOT that the accused wrote them.
The op would have a fairly strong case in a civil court in front of magistrates but a criminal case the CPS would not bother... its as simple as that.