  The Particle Flow (PFlow) approach to calorimetry promises to deliver
unprecedented jet energy resolution for experiments at future high energy
colliders such as the proposed International Linear Collider (ILC). This paper
describes the PandoraPFA particle flow algorithm which is then used to perform
the first systematic study of the potential of high granularity PFlow
calorimetry. For simulated events in the ILD detector concept, a jet energy
resolution of sigma_E/E < 3.8 % is achieved for 40-400 GeV jets. This result,
which demonstrates that high granularity PFlow calorimetry can meet the
challenging ILC jet energy resolution goals, does not depend strongly on the
details of the Monte Carlo modelling of hadronic showers. The PandoraPFA
algorithm is also used to investigate the general features of a collider
detector optimised for high granularity PFlow calorimetry. Finally, a first
study of the potential of high granularity PFlow calorimetry at a multi-TeV
lepton collider, such as CLIC, is presented.
