Defend this case as the representative of the employer against the plaintiff (Charles) in accordance to UK statutory law and case law? In depth law based analysis and best argument I could use (law argument).

Charles Parker is an experienced Accountant in the Accounting Department and has generally been an exemplary employee for the past 11 years. However, he is now suffering from depression since the cessation of his intimate personal relationship with his partner/boyfriend, Jim, and with whom he also worked closely and in the same department; consequently, his work has deteriorated. Charles asked to be moved to the Payroll department in order to be away from Jim but this has led to more problems since he was unable to master the computer system used in the Payroll department. Whenever training was offered, Charles was off work, feeling unwell. He has also proved unpopular with the staff in his new department because he talked constantly about the relationship break up with Jim, even after his manager warned Charles that he should keep his private life to himself. Charles made an effort to do this but felt persecuted because other members of staff were allowed to talk about their private lives. He then made an error entering the payroll details to the company bank, which resulted in staff being paid 3 weeks late; when this error was realized by the company he was sacked immediately.