Time was, if you denied that gods existed loudly and publicly enough, you were considered a threat to the social fabric and arrested under blasphemy laws. This Wikipedia page mentions James Naylor, who in 1656 suffered flogging, branding and the piercing of his tongue by a red-hot poker.

No more. The little-used and anachronistic blasphemy laws have been revoked.

After an acrimonious debate in which the bogeyman of secularism was repeatedly invoked, the House of Lords on Wednesday March 5 2008 accepted the amendment to the Criminal Justice and Immigration Bill that abolishes the common law of blasphemy and blasphemous libel.

I liked the comment from the Earl of Onslow:

On the question of blasphemy, it has always struck me that if Jesus Christ exists, and if Jesus Christ in his Godlike form was capable of creating the universe, then he could quite easily hack the bit of left-wing obscurantism and b-mindedness that writes things such as “Jerry Springer: The Opera”. If he does not exist, nothing will happen; if he does exist, it is up to him to get hold of the chap who wrote it and make sure that he does time in the diabolical house of correction. The offence is unnecessary.

It also seems that the provision applies only to the Church of England, not to the doctrines of the Roman church, as far as I can gather. You can be just as rude and insulting as you like about the doctrine of the Assumption of the Blessed Virgin Mary, papal infallibility, or what the Church of Rome says about contraception; you can be blasphemous about those without any possibility of being prosecuted.

Blasphemy is a crime that is open to intense mockery. As the Minister said, something that is open to mockery and has been used only four times since 16-something-or-other has no place on the statute book.
…
Please let us now get rid of the crime of blasphemy. It is unnecessary and otiose.

Not everyone was happy.

Lord Armstrong of Ilminster: …The fact that one has not had a flood for a very long time does not mean that one should destroy the floodgates. My fear is that the removal of this provision will be seen as encouraging people to make outrageous statements that are needlessly offensive to a great many people. They will only do it to annoy, because they know it teases.

He then burst into tears, sucking his thumb while rocking and whimpering quietly to himself.