Complex sentence: The painting was in the ownership of Richard Robert Graham, depicted on the far right of the painting, at least until his death in 1816 then went via several owners to Lord Duveen who presented it to the British National Gallery in 1934.
Split into simpler sentences: The painting was in the ownership of Richard Robert Graham, depicted on the far right of the painting, at least until his death in 1816. It then had several owners before it was acquired by Lord Duveen who presented it to the British National Gallery in 1934.