Is there a method of translating RAL colours to Pantone colours or vice versa?

No, as these are entirely separate colour systems there has been no collaboration to produce a chart for translation from one system to another. Other companies (particularly paint companies) have attempted to cross reference these and can be found on the web but usually only offer alternatives for RAL Classic colours and the matches have not been quality checked so many are quite far apart in colour space.
We recommend that you purchase the relevant RAL Guide and Pantone Guide and check yourself under controlled lighting conditions in a light box.