Is linking R to a vowel in British English an intentional effort or a natural oc...

If I am not wrong, the linkage between words happens naturally when you try to pronounce the words quickly. Unlike American English, where the ending R is always clearly pronounced, British pronunciation has very specific rule that the ending R is only pronounced when it is followed by words starting with a vowel. I wonder if this linkage in British English in particular is a conscious and intentional action that only happens after at least some processing in the brain.

Also, take the words "grandpa" and "grandfather" as an example, they both end with a vowel in British English when pronounced alone. However, while I know British English speakers are fine when saying "Grand[pa] [is] sleeping" , I wonder if they feel unnatural when saying "Grandfatha [is] sleeping", i.e. with completely silent R, instead of "Grandfatha "ris" sleeping" (in a normal speaking pace and flat tone where the "is" is not specifically stressed).

Many thanks in advance for helping me on these 2 questions.

Edit: I apologize that this is not a good example as it has the option of contraction, i.e. "Grandpa's sleeping", which I think should be way more commonly used, but it is not the main point of this post, so please bear with me on this.

I have just tried it and I say /ˈɡrændˌfɑːðə.ɪz/ with no linking /r/. This sounds perfectly natural to me as a British English speaker (Gen Z, southern England).

In British English most speakers do not perceive the ‹r› as silent where it's dropped postvocalically. For example, we perceive /ɑː/ as "saying the r" in ‹ar›. A nice example is this comment on a Facebook post on the word ‹arm› /ɑːm/: "How the hell do you say arm without pronouncing the R lol? Am as in ham?".

Similarly, in ‹grandfather› /ˈɡrændˌfɑːðə/, the ‹r› isn't perceived as silent.

As this Reddit comment observes: "Most Brits won't even accept that they don't pronounce the Rs because they don't hear it like that ... there's Brits who will swear blind on their nans grave that they pronounce every R".

It feels to me like there's perhaps a slight aspiration or heaviness to the end of ‹father›, ‹farmer›, ‹bother›, ‹lover› that isn't there in ‹comma›; or maybe the vowel is a little further back. I'm not a linguist and that could be a complete hallucination – I'm just offering it as an example to show that the words "feel" different; that I "experience" myself as pronouncing the ‹r›.

Consequently, nothing is missing for me when I say /ˈɡrændˌfɑːðə.ɪz/. The ‹r› isn't silent. Or – you know, I'd never think about it that way.