Anyone who works in wildlife rehab will tell you what difficult "patients" wood pigeons are. They can get so stressed just by the mere sight of a human that they may injure themselves by throwing themselves into walls or by generally thrashing in a panic. We often have to keep all contact with them to an absolute minimum and screen them off so that they are not able to even see humans, as it's just too distressing for them.
Not this little guy who has come in this evening, however - he is calm around people and eager to hop onto our volunteer's hands. This strongly suggests that he is tame, or "imprinted", and the most likely explanation for that is that a well-meaning person has raised him from a young age, and then released him into the wild.
This is one of the reasons why we strongly advise that the public don't attempt to rear animals themselves. For a chance at succsessful return to the wild, animals need to be reared with members of their own species, they cannot be cuddled or socialized too much by humans, and they often need to gradually be re-introduced to the outdoors and to independent living over a period of weeks via a soft release aviary. They can't simply just be let go.
An imprinted animal has poor survival instincts. It doesn't know how to interact with its own species, or how to find food or shelter - it has grown accustomed to humans providing these things. Worse still, it will have no fear of humans, making it very vulnerable to the many nasty individuals out there who choose to harm wildlife.
Sometimes, we can "re-wild" animals by putting them with members of their own species, withdrawing all contact with humans, and giving them plenty of time to adjust to the outdoors in an outside aviary. Unfortunately, however, imprinting is not always reversible, so some animals are rendered unreleasable for life. Yes, they may live longer in captivity, but they may also be deprived of the experiences that make a wild animal's life rich. Like the sheer joy of being able to fly free, of interacting with their own species, of all the elaborate rituals involved in finding a mate and mating for life, and of foraging for food - whilst food is plentiful in captivity we can't replicate the variety of a wild diet. And so on.
We know it's hard to find a rescue placement in SE London with so few rescue organisations in this area, and with the few that are within reach often being full up and overwhelmed. But there is always a way to get to a rescue that can help if you're just willing to make enough phone calls, pay for a cab, jump on a train, whatever. So we strongly advise being persistent about finding a reputable rescue rather than attempting to rear animals yourself. That is what's in their best interests.