1. The British needed to have the support of the Dutch in the event of a common enemy.

(This is only 1 answer.)

If referring to what western country(s) conquered Malaysia;

In 1511, Malacca fell into the hands of the Portuguese and that was the beginning of the colonial era in Malaya. After that, Malaya fell into the hands of the Dutch in 1641 and British in 1824 through the Anglo–Dutch Treaty.

Anglo-Dutch Wars happened in 1652.

Fourth Anglo-Dutch War happened in 1780.