The British government at the time made sure not to see how "neutrality" was being violated--in spirit, if not in letter.   Adams, the US Minister to Britain,   tried many times to try to persuade the Palmerston regime to block at at least three ships built in Britain for the Confederacy from leaving the UK. It was an open secret that they were built to ravage "the commerce of the North", as the song goes --though only supplied with guns outside the 3 mile limit.

How many specific instances of refusal to take action do you need?   There is a long list.

The government finally did block the "Laird rams", but, it appears, only when faced with the strong possibility that if it did not, the Lincoln administration might well send US Navy ships up the Mersey to destroy the "rams" before they were launched.