Read this and answer the question. If the question is unanswerable, say "unanswerable".

After the grant of the royal charter it had become known as the Royal Institute of British Architects in London, eventually dropping the reference to London in 1892. In 1934, it moved to its current headquarters on Portland Place, with the building being opened by King George V and Queen Mary.

Who opened the structure in which the Royal Institute is formerly housed?
unanswerable