Received Pronunciation (RP) has a complicated relationship with the idea of “standard English” in England, and the answer depends on what you mean by “standard”.

RP is often described as the prestige accent of England, and it’s the accent traditionally used by BBC newsreaders, the monarchy, and educated speakers from the south of England.

It’s also the accent most commonly taught to foreign learners of British English and the one used as a reference in many dictionaries.

However, calling it the “standard” is somewhat misleading for a few reasons.

First, it’s not actually spoken by most people in England. Estimates suggest only around 2–5% of the population speaks RP as a native accent.

It’s largely associated with a particular social class and regional background (primarily southern England and elite educational institutions like Oxbridge).

Second, England has enormous dialectal diversity, and no single accent has ever been universally adopted across the country in the way, say, General American has become somewhat of a default in the US.

So the more accurate picture is that RP functions as a prestige accent and a reference point for formal or media use, but it isn’t a nationwide standard in the sense that most English speakers in England actually use it day to day.

Many linguists would distinguish between Standard English as a set of grammatical and vocabulary norms (which can be spoken in many different accents) and RP as one particular accent that carries social prestige.

You can speak Standard English grammar without using an RP accent, and plenty of people do.

In recent decades, RP has also been evolving and loosening up somewhat, with a broader form sometimes called “Received Pronunciation” blending with other accents, particularly in younger speakers.