Act of Settlement

From the UK :

"The Catholic Church last night welcomed moves by the government to draw up plans to change the Act of Settlement, which bans Roman Catholics from becoming king or queen.

Jack Straw, the Justice Secretary, is working on plans to alter the 307-year act, which would also allow a king or queen to marry a Catholic, a Cabinet minister said yesterday."

Read : http://thescotsman.scotsman.com/latestnews/We-welcome-bid-to-end.4782074.jp.

I'm slightly confused. Can someone explain to me the relevance of this move in the year of Our Lord 2008 ?