From the Independent:
At the height of sanctions against Yugoslavia, SIS, the secret intelligence service, warned No 10 about a similar donation to the Conservative Party from a Serbian source. The concern of SIS at the time was that this could be used to compromise the party.
Now, the Conservative Party is already highly compromised by its unfortunate Russian connections. In the Parliamentary Assembly of the Council of Europe, which is supposed to promote human rights, Tory MPs have, until very recently, been closely allied with the United Russia Party of Vladimir Putin.