An independent assessment of the physics of Ignitor ispresented. Ignitor is a physics demonstration experiment with the main goalof achieving thermonuclear ignition, defined as the regime wherefusion alpha heating compensates for all forms of energy losses. Simulations show that a pulse of alpha particle power of up to 10-20 MW is produced for a period of more than a few seconds. Crucial issues are the production of peaked density profiles on atimescale of several energy confinement times, the control ofcurrent penetration for the optimization of ohmic heating andsawtooth avoidance. The presence of a 10-20 MW ICRF system and the operation of a high speed pellet injector are considered essential to provide added flexibility in order tocounter unexpected, adverse plasma behaviour.