The Trust has released a statement saying Maria Ball has resigned with immediate effect.
The process for appointing a new or interim chair will be started immediately but in the meantime Paul Remington who is vice chair will lead the organisation with Andrew Morgan, the interim chief executive.
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John Willis was born without fully formed arms and legs but set himself the task of participating in all 34 Olympic and Paralympic sports.
England captain Dylan Hartley lasted just six minutes off the bench after he was red-carded in Northampton Saints' defeat to Leinster.
Cloudy for most through Saturday with early intermittent rain becoming heavier and more widespread later. Drier and brighter on Sunday.