YANBU. I rent in London, currently looking for a new place and speaking to lots of agents about the market. They all are very clear that over the last year rents have fallen. So unless the place you are in was massively below market value when you moved in, it is now worth less money, not more.
Even if that wasn't the case, and it very definitely is, a rise annually is not standard. If you are there a very long time then a raise may be requested at some point.
Your landlord may be ignorant or may know but be hoping you will want to avoid the hassle and cost of moving. The fact is that the market is quite slow and he has much more to lose from the property being empty even if just for a couple of weeks. He would also almost certainly have to re let the property at a lower rent than you currently pay. You on the other hand could possibly get a better place for what you currently pay than you did a year ago.
I would be tempted to show great surprise and say that given that rents have fallen you will have to reassess your position. You could suggest he speak to an agent for advice, they will tell him this. There is a danger he might not renew the contract, so if you really don't want to leave be aware of that risk. I would be minded to not accept the rise and leave if he holds out. I know only too well how difficult looking for a rental and moving is in London, but still.
If he agrees to a smaller increase that you could accept, even though you should not have to, because you'd like to stay, make sure you pin a condition on it of any maintenance or improvement you need.