  For almost 50 years the structure of the Lambda 1405 resonance has been a
mystery. Recently, a new lattice QCD simulation showing that its strange
magnetic form factor vanishes, together with a comprehensive Hamiltonian
analysis of the lattice QCD energy levels, has unambiguously established that
the structure is dominated by a bound anti-kaon--nucleon component [1]. Here we
present supplementary information for Ref. [1] including a presentation of the
relevant Hamiltonian effective field theory and an illustration of the volume
dependence of the results and their connection to the infinite volume limit of
Nature.
