@Thelifeofawife - I agree with other posters - get a hotel close to the venue that you can walk to but keep phones out of sight on the street, (even during the day).
I would also suggest using a crossbody bag with a zip and not putting wallets/phones in jeans pockets!
There will be loads of people pouring out of the venue at the end of the concert, so you won’t be wandering around on your own.
I would suggest using the toilets before the end of the concert, though - this avoids queues and makes sure that you leave at the same time as everyone else!
Edited to add:
DS2 got his phone snatched at Oxford Circus the other day by a thief on a bike. He had the presence of mind to shout that someone had stolen his phone and, rather unbelievably, a guy on a motorbike gave chase. The thieving scum bag then panicked and threw the phone on the ground.
On a related note:
I don’t know how many times I have told adult DS1 & 2 to keep phones out of sight, but it’s like talking to the wall 🙈 DS2 is now being more careful- I think 🤞