Jaywalking in England

In America, jaywalking (crossing against the light or in the middle of a block where there is no marked pedestrian crossing) is technically illegal, but the enforcement rate is generally^* very close to zero. I tend to cross the street when it's convenient and looks to be safe to do so^**, not when I reach an intersection and the light is green.

We'll be traveling to England (London). While we're there, we'll be doing a lot of walking, and I'll be going for at least 1 run.

I'm sure that jaywalking is probably just as illegal in England as it is in the USA, I'm curious to know if the enforcement rate is generally^* very low there (particularly in those cities), as well, or will I need to alter my procedures to not run afoul of the local constabulary. Last thing I want is any sort of legal trouble while traveling...

^* I say generally because I know that's very dependent on the exact day and time, the mood of the officer who may happen to notice the offense, and, possibly the phase of the moon and recent sun spot activity. If the answer is "No, it's not enforced", I realize that the answer will generally apply and that these things may will factor in as well. I recognize that if I chose to break the law based on suggestions here and get ticketed for it, "Travel.SE user X said it was OK", will most likely not hold up in court.

^** I learned the skill from my parents and grandparents in midtown Manhattan where one crosses the road whenever the traffic is stopped (which is often) and one wants to get to the other side. Walk to the corner to cross the street? Then walk back? My bagel shop is straight across the street, why would I do that?