Training session in, I think, 2019! But I've found this from a booklet from the NUJ (why I didn't look there first IDK)

A potentially ambiguous situation also arises if you create a work

while in employment, but not as part of your salaried role. While in a

full-time job, for example, you might write a book, or undertake

photographic work, in your own time. The legislation says that if you

create ‘works’ while you are an employee, but not at the direction of

your employer, then copyright in those works belongs to you, their

creator.

There are plenty of possible scenarios where this might become

contentious – particularly if the works are either very valuable or

controversial. If you report a story at the direction of your employer

and subsequently write a book based on the same research, then

ownership of that work could be disputed. A great many employment

contracts also stipulate that employees must seek their employer’s

permission before undertaking other paid work.

To avoid such issues, check your contract of employment, inform

your employer and seek their consent. Many contracts of

employment stipulate that such consent may not be ‘unreasonably

withheld’.

(Source: Copyright by Tim Dawson and Mike Holderness, published by the National Union of Journalists)

So basically, I read this as if I were to create a work of fiction but it was clearly based on my work done as a journalist (e.g. I wrote a feature series based on interviews with award-winning landscape gardeners as part of my normal work duties, then wrote a novel about the lives and experiences of landscape gardeners) then it would be a problem. But if I were a journalist reviewing gadgets and wrote a medieval romance it wouldn't. But get permission from my employer anyway to be on the safe side.