What? Has it been growing through the window to inside the room? Is that window broken to where that can happen? Or is the window open? In any case rip the plant out and then have the one responsible for the property make repairs ASAP.

Looks like a buddleja davidii which is quite rampant and the roots find the smallest cracks to root into. You often see them on house roofs , chimneys and gutters. I think it's a case of just cutting it off in bits and teasing the root out from wherever it is growing. Then inspecting the damage!

Indeed! Never seen anything like it before. The growth source is from inside the living room wall, probably under floorboards - through the brick/stone and the trunk which is some 10 cm wide then protrudes through the wall / window thereby pushing the window and frame inwards creating a large gap between. If can identify precisely the species will be able to know how to contain or remove and repair damage. The plant has been cut back now to the window level with the trunk showing and new leaves now sprouting.

welcome to GoY. yes it looks like a buddleia . remove as much as you can and trace the stem back as low as you can the use sbk root and stump killer to kill it off.

Honeysuckle has identified the species, but the treatment would be the same for anything that has done this. Once its been cut off at both sides of the window and then cut again near floor level you can decide what to do - either use SBK stump killer or take up the relevant floorboards and cut it off below the growing point. You'll have to take up the floorboards to remove the stump anyway eventually if that's where the root is...

Thank you all for your prompt and expert advice. Much obliged.