Safari / Chrome Browsers opening links in new windows / or reading list

I've recently upgraded from a venerable iMac to a MacBook pro running Sonoma. However, for whatever reason, the following is happening when using Safari or Chrome:

In Safari:

1. Clicking on links, doesn't open anything, it just adds them to the Reading List;
2. When I open a new tab, Safari doesn't let me view it

In Chrome:

1. Every link I click on is opened in a new window

Any help would be greatly appreciated as it's really making it a chore to browse on the machine at the moment - to the point where i'm mostly using my phone.

Kind regards,

Graeme