What to do when feral kids approach you?

Yesterday, I've had "feral-kids" incident for the first time ever in my life. The bizarre thing about it that it happened in Belsize park/Primrose hill area on my way back home. Now, it's a very safe area, partially "posh", you'd never expect some kids in grey tracksuits smelling substances walking around and harassing people in here. I'm a woman, moved here recently, no idea which corners of Primrose hill/Belsize Park to avoid not to see these ferals again?

They were harassing people, myself, Starbucks barista on England's lane. I was scared so badly that I went in the pub in front of Starbucks and hid there for a bit until they left the area.

What are you supposed to do, how are you supposed to behave when you see such kids? What to do if you're approached by them directly? Are there any rules for safety in such situations? Are you supposed to take all insults, harassment, physical intimidation and look down to stay alive? They didn't touch me, but a boy came very close to me to say smth - I was stuck in shock.

P.s. a man who was outside the pub drove me up to next station so that I didn't have to walk alone in distress. I can't thank him enough for this!

Edit: thanks a lot for good suggestions on carrying safety devices and pointing out at areas to avoid :)

Also, this topic made me realise how "class" problem is pushed into any discussion in the UK subs as it's such a sensitive topic for locals. Making everything about class and hating people for their postcodes seems prevalent, it seems like it's a big trigger point. So, to clarify things I'll put it here: "feral kids" term is used for offense, not class and financial background. No, I don't apologise for living in this postcode and loving it for its safety and parks and infrastructure. I also don't apologise for someone feeling insecure about their economic situation and putting so much hate on young professionals from higher paying industries. We're all surviving. Peace!