BBC News - MI6: Richard Moore named as new head of Secret Intelligence Service - some of my analysis inside the piece on what the job will involve - balancing the internal and external demands of running the service https://www.bbc.co.uk/news/uk-53582938
China will likely dominate Richard Moore's agenda as Chief of MI6 - building up the intelligence coverage on the country and also maintaining alliances within the Five Eyes community and expanding them to other countries as well.
In order to keep producing intelligence, MI6 will also need to keep modernising. As I wrote a few years back, the power of data to uncover secrets- including identities - risks destroying agencies who do not change https://www.wired.co.uk/article/spies-data-mi6-cia-gordon-corera
Moore will also have to navigate a spending review and work out how closely to align himself with the rest of Whitehall and government. MI6 Chiefs used to keep their distance but in recent years have been drawn closer, too close some said in the case of Iraq
For those after a bit more on the history of MI6 there's this book - a bargain on Kindle..... https://www.amazon.co.uk/MI6-Death-British-Secret-Service/dp/0753828332
Or if you prefer Radio Documentaries, there's this series made for @BBCRadio4 when MI6 hit 100 years. https://www.bbc.co.uk/programmes/b00lrsnk