You can only enter a building and claim squatters rights if there is no forced entry, i.e. if there is a window open, and they can get in, without breaking and entering, then I believe they can claim squatters rights.
However, there's been several cases where squatters have committed breaking and entering and repaired the damage and said to the authorities, that the door was ajar. Hard to prove otherwise.
Laws have changed since the early 80's, when it was ridiculously easy to claim squatters rights, but you still can. I actually lived briefly in a squat in London in the early 80's; a council block of flats due for rebuilding. Was a bit of fun for a few weeks, but no water,m no electricity, etc, wasn't all that after a while.
I think the courts are far likely to side with a home owner nowadays. I have a gert alarm on the house now, which reports B&E when i am away, if it were to happen, so I have a legit come back. This is ambiguous - Whilst people can enter my property whilst I am away, it is very easy to remove them
Land Registration Act 2002
Allows squatters to apply to own the property if they have lived there for 10 years.
Under the terms of the Land Registry Act 2003, "squatters" are permitted to enter an uninhabited property and apply for ownership after the 7 year period under the following conditions:
(1) They did not break in to the property (doing so is a criminal matter and they could be prosecuted). Basically, they have to have to entered the property by simply opening the door.
(2) They have to prove that they have lived in the property for that time and produced gas, electricity and water bills and dated pictures.
(3) They have to have a key to the property, allowing them unhindered access in and out of the building.
(4) The property cannot have been furnished by the "previous" owners, prior to them inhabiting the property.
(5) They can proove that they reasonably believed that the property belonged to them during this time.
(6) The owners are notified and have the right to fight them in court.
Most importantly though, Occupiers of non-residential properties and those who are not displaced residential occupiers or protected intending occupiers of residential properties can’t force their way into a property when someone there opposes entry.
What that means is that if you live in the house, come back and find someone in there, you are a displaced resident and can apply to the police to get them removed, which could take a few weeks. However, if you own rental property's, and don't live there, you cannot force the door down and remove the squatters.
Interestingly, there are no 'squatters rights' in Scotland.
Can squatters take ownership of a property?
The process for someone who isn’t the legal owner of a property to take ownership after living in it for a certain amount of time is called ‘adverse possession’. It is very rare for squatters to be able to do this because they have to stay in a property without the owner’s permission for at least 10 years.
The amount of time a squatter needs to stay in a property before they can get ownership depends on whether the land is registered or unregistered.
If the land is unregistered, a squatter would generally need to occupy it for 12 years to get ownership. If the land is registered and a squatter lives there for 10 years, they can apply for registration. The current registered owner will be able to object and in most circumstances will be able to stop squatters from taking ownership.
Section 6 of the Criminal Law Act 1977 makes it an offence to force entry to a building which is occupied, and this includes squats.
Squatting is legal because trespassing is not a crime in English and Welsh law. Trespassing is a civil issue, a dispute about who has the right to the land or property, to be settled between two individuals in a civil court. It has nothing to do with the criminal law.
Squatters also rely on section six of the Criminal Justice Act 1977, which makes it a criminal offence for anyone to break into a squat or any other home as long as someone is inside who is opposed to their entry. The police have no more power to enter a squat than any other home.
Finally, hit is a legal defintion of what are squatters rights:
I think that should cover it all.