He beat Jeremy Hunt in a ballot of party members and will enter Downing Street on Wednesday.
With temperatures set to soar in the coming days, how can the UK keep cool and carry on?
The Labour leader says he wants to "confront this poison and drive it out of our party".
Campaigners say investigations have stopped after complainants refused to hand over their devices.
The university, which alerted police, was subject to a "sophisticated and malicious" phishing attack.