Although with tenanted property there is currently no legal requirement for an electrical safety certificate (except in the case of all HMOs) it is now widely accepted in the letting industry that the only safe way to ensure safety, and to avoid the risk of being accused of neglecting your 'duty of care', or even of manslaughter is to arrange such an inspection and certificate.
So, as long as everything works then thats fine. It doesnt mean it has to be safe and 100% to the regs.
Although if there was a dangerous installation, then the landlord has a duty of care and if nothing is done, he may become liable should anything happen