After leaving Dohm, he was appointed secretary and chief accountant of Park Royal Vehicles, a wholly owned subsidiary of ACV Group.
Whilst working for AEC as a director, Slater fell ill and during his recovery became interested in investing, and developed a system for picking stocks which would much later form the basis of his book The Zulu Principle (1992).
He then approached his friend Nigel Lawson, at that time the City Editor of The Sunday Telegraph, and was hired to write an investment column under the pseudonym 'Capitalist'.
Slater Walker then changed strategy, from a corporate-conglomerate into what eventually was recognised as an unauthorised and unlicensed international investment bank, through gradual disposal of its industrial interests.
Slater resigned as chairman in October 1975 due to extradition attempts from the government of Singapore for the alleged misuse of more than £4 million of company funds in share deals.
[4] However, the court accepted that the offences were purely technical, that Slater had not acted dishonestly and that there was no question of him having made any personal gain through committing them.
These tactics proved to be highly successful and profitable in the short-term, such that "Slater Walker" became a byword for a particularly forceful and financially rewarding form of capitalism.
Some years later, Slater acknowledged the drawbacks that were inherent in the practices he adopted, towards the end of an interview with Hunter Davies in The Independent published on 15 December 1992.
[8] Slater was also the author of a book on investment, The Zulu Principle, which focuses on simple techniques for identifying small dynamic growth companies whose shares are at a low price compared to their future prospects.