The best £20 power bank to charge a phone?

I've got a fairly generic one (can't even remember the brand) as a present for Christmas and it does the job well.

If I were to buy myself I think I'd look at Anker ones to start as I've heard pretty good things about them.

On a tangent, I've seen a crazy rise in the number of people with phone cases that include an external battery. Not only in person but also in films and TV shows. Before everyone seemed to be obviously using a Samsung/iPhone but now I keep seeing the phones covered up by big clunky cases providing extra power! Perhaps Anker have got into the product placement market

Anyway, I think this offer is still running and worth checking out: https://www.latestdeals.co.uk/deals/anker-power-bank-20-off-amazon-uk

I've got Anker and it's great!

I would get an Anker, does the job as well as any other in the price range if not better and customer service is spot on if you need them.

I got a friend one of those phone cover battery pack thingys, Kiwibird brand, and he said it was really good. You can get pretty thin covers like this now, you charge them up and then when you need the extra power you just press the button and it starts using the battery that is built into the cover. He was barely getting through a day with his regular phone battery, once he started using the case I got him he was getting through two days without having to charge! Might be worth checking them out!