Gay and bisexual men who use apps to meet strangers for sex have been warned about personal safety fears following the conviction of serial killer Stephen Port.
Police stressed that users should meet in a public place for the first time, not someone's home, be careful about what they eat or drink in case it has been spiked with drugs, and tell someone else where they are going.
Detective Chief Inspector Tim Duffield, who led the successful investigation into Port's string of killings and sex attacks, said: "From my perspective, the advent of social media platforms has made it really, really easy to hook up with people anonymously.
"Although the vast majority of interactions that users will have will be completely safe, people need to know that they should take precautions to keep themselves as safe as they possibly can."
Port met his victims via social media. Investigators found at least 25 accounts that he had used with different names, and had to examine 100 media devices as part of the inquiry.
The horrifying deaths also shone a light on so-called chemsex - where gay or bisexual men take disinhibiting drugs as part of sexual encounters.
Scotland Yard Commander Stuart Cundy warned there is a "fine line" between what is thought to be "safe" use of the drug GHB, and death.
He said: "There is such a fine line between using it for heightened sexual acts, through to unconsciousness, through to death. It is a real fine balance.
"GHB is a dangerous drug. For those that use it, they will understand that there is always that fine line. In the case where it's not just been taken once, it's been taken again, so what might be considered a safe dose at one point is then added to by taking it at some point in time later, you need to be a very proficient medical expert to truly understand what would be safe and what wouldn't be safe."