Engine number on Engine different to Registration

I purchased a vehicle from the widow of a friend who passed away.<br> When I took it for roadworthy, I found the Engine number on the engine is different from that of the registration papers.<br> My friend did not change the engine, so I approached the dealers he bought it from.<br> I tried to call Top Gear and received only a \fax tone"from the number listed.<br> I then mailed them"