If an employer chooses not to provide any training can an employee dismissed for unsatisfactory job performance succeed in a claim for unfair dismissal?

Yes, the fairness or otherwise of an employee's dismissal for incompetence will be determined in large part by evidence of the employer's failure to provide appropriate training. An employer's failure to supervise, train and encourage a new (or newly promoted) employee is one of the factors that tribunals will take into account when considering the reasonableness of an employer's decision to dismiss.