A BMRA member has been in touch to make others aware of fake catalytic convertors (cats). 
The cats are being tampered with and the tops/bottoms of them are being cut open and the precious metals “ biscuit “ is being removed from inside and replaced with low or no value catalysts. The centres have then been filled with stone/brick and welded back together.
The cats also appear to have been covered in oil/mud to hide the new welds to make them look genuine.