The book I have says the Corn Laws were repealed in 1846 as a response to the famine but doesn't bother to discuss the effect of that - e.g., whether it took four years for the effect to percolate sufficiently through the system to make a difference.

My book is written by someone who would really like to thoroughly blame the British but can't quite find the evidence to do so. I shall look into the Corn Laws further, I think.