Mervyn Kohler, special adviser to charity Age UK has told ITV London that heat can be "stressful" for older people, as scorching temperature continue across the UK.
Mr Kohler said: "For God's sake, let's enjoy it, you have to act sensibly and responsibly, and enjoy the warm weather".
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"All it takes is for somebody to see me - and I could just die, just like that. I could want to go to the shop and not come home."
Before the killing, Peters searched the internet for "serial killers", "treatment of child killers in prison" and "premeditated murder".
Arriva Rail North, Greater Anglia and South Western Railway are all affected.