I've spent my entire career in the third sector, including 32 years as a chief executive. It hasn't always been easy, but has always been worthwhile.
I've been able to advance many causes, including campaigns to end apartheid, the death penalty and torture. I've also been involved with causes such as HIV/Aids, climate change and its impact on children, and the plight of refugees. I've had the privilege of leading four fantastic organisations, helping them raise close to a billion pounds, including vital contributions to many humanitarian emergencies.
I've visited about 70 countries and seen much suffering but much more joy, courage and determination. I've been inspired by the belief, commitment and positive power of young people. Much has changed for the better: apartheid is over, the Berlin wall fell, democracy replaced dictatorship across Latin America, under-five mortality has halved. There remain huge challenges, but the benefit of a long view gives me grounds for optimism. Charities have a vital role to play and need to be supported, empowered and defended. Aid works - we need more, not less.
I am proud of the contribution I've been able to make and will continue to do what I can. I was asked recently what advice I would give to someone aspiring to lead a third sector organisation. My response: success comes from everyone in your organisation working together. You must inspire them, look after them, build a positive, empowering culture; be bold and ambitious. You must challenge when necessary, but always with respect and honesty. And you must empower your supporters - nothing is possible without them.