Has iPhone security been compromised by the UK government?

CNET – Apple Pulls iCloud Encryption Feature Following UK Government Demands

"The company said it was "gravely disappointed" to no longer be able to offer Advanced Data Protection to iPhone users in the UK."

Not without Apple’s assistance compelled with a court-order.

UK residents still have the “Standard” Data Protection described in link below.

What has been disabled is the ability to sign-up for “Advanced” Data Protection.

iCloud data security overview – Apple Support (AU)