QUOTE: “There’s probably always gonna be a little bit of room for keyword research because you’re kind of providing those words to users. And even if search engines are trying to understand more than just those words, showing specific words to users can make it a little bit easier for them to understand what your pages are about and can sometimes drive a little bit of that conversion process.  So I don’t see these things going away completely but I’m sure search engines will get better over time to understand more than just the words on a page.” John Mueller, Google 2020
If you want to *ENSURE* your FULL title tag shows in the desktop UK version of Google SERPs, stick to a shorter title of between 55-65 characters but that does not mean your title tag MUST end at 55 characters and remember your mobile visitors see a longer title (in the UK, in January 2018). What you see displayed in SERPs depends on the characters you use. In 2020 – I just expect what Google displays to change – so I don’t obsess about what Google is doing in terms of display. See the tests later on in this article.
The SEO starter guide describes much of what your SEO will do for you. Although you don't need to know this guide well yourself if you're hiring a professional to do the work for you, it is useful to be familiar with these techniques, so that you can be aware if an SEO wants to use a technique that is not recommended or, worse, strongly discouraged.