How to convince my parents to let me go to london?

Hey :D I'm 14 and I want to go to london to see this slipknot exhibition however it would be awkward if my mom was there because I'm meeting my boyfriend there. Don't say I'm to young because i'm not :3 I properly love him and he loves me <3 Anyway It will be really awkward if my moms there but what do i say to here P.S moneys not a problem and shes usually not strict :D Btw I live in england about 2 hours away from london :D