A horse has been rescued by the RSPCA after concerns were repeatedly raised by residents.
The RSPCA earlier this year began monitoring the welfare of three horses on a plot next to Chingford Rugby Club in Waltham Way, Chingford.
The charity has now revealed that, due to "health concerns", a female chestnut horse has been removed from the muddy field and is now the subject of an investigation.
A spokeswoman said: "A horse was recently rescued from the field on veterinary advice due to health concerns.
"The other two horses were checked by a vet and appeared to be in reasonable condition.
"Our inspectors continue to monitor conditions at the field.
"The female chestnut horse is currently in our care and she appears to be recovering well.
"As this is an ongoing investigation we would be unable to comment further at this time."
According to residents and animal activists, a grey horse previously confined to a small fenced area due to a number of escape attempts, has not been seen for weeks.
The RSPCA has refused to comment on the whereabouts of the grey horse or the condition of the removed horse, prior to their intervention with the assistance of the police on April 16.
Former horse-keeper and resident, Maureen Turner, of Sewardstone Road in Chingford, has contacted the RSPCA on several occasions.
She said: "It is sad that one of them had to become seriously ill before they intervened.
"The way they've handled the horses is wrong but I hope the RSPCA will take notice now.
"The owner doesn't deserve to own animals and his attitude is, he doesn't want our help.
"Up until the rescue, the RSPCA had acted as though they weren't interested and it has been a nightmare in terms of trying to find out the truth."
The RSPCA spokeswoman added: "we appreciate members of the public helping us look out for the welfare of these horses and if conditions deteriorate, we urge people to ring us on 0300 1234 999."