Who is the richest BTC holder?

Can you enlighten me on the identity of the individual or entity that currently holds the largest amount of Bitcoin (BTC) in their possession? Is it an individual investor, a cryptocurrency exchange, or perhaps a government entity? And what methods have been employed to estimate the wealth of these BTC holders, given the pseudonymous nature of Bitcoin transactions? Furthermore, has there been any significant changes in the ranking of the richest BTC holders over time, and what factors might have contributed to such changes?