Complex sentence: In 1905 he was offered a promotion and a transfer to Haulbowline Island, but declined on the grounds that this entailed enlisting in the Royal Navy, albeit in a purely administrative role.
Split into simpler sentences: In 1905 he was offered a promotion and a transfer to Haulbowline Island. He declined on the grounds that this entailed enlisting in the Royal Navy albeit in a purely administrative role.