Truth (in English law) is merely a defence to an accusation of libel or slander, and it is not an absolute defence. If you say or print true things about a person, that lowers their reputation in the eyes of an ordinary person, and you are motivated by malice, then you have still committed the crime of defamation.

English libel law is an evolution of the former English law known as scandalum magnatum -- "scandalizing the mighty". Basically, if you say bad things about powerful people, those powerful people will crush you with the law.

As an example, Robert Maxwell embezzled millions from his company's pension fund, and also used that money to sue anyone who slighted him - including anyone who said he was embezzling from his company's pension fund. He was never prosecuted for embezzling millions from his company's pension fund.