Your lawyer should advise you but ultimately follow your instructions. If he feels (or knows) you are guilty and you want to plead otherwise, he should decline to represent you.
... or resign.
There are lots of instances in professional services where you simply have to say 'no'. If you're not willing or able to represent your client in the way they want to be represented, the correct response is, "I'm sorry, but I'll be unable to continue to advise and represent you on this matter."
In the doctor example above, the doctor will—and should—absolutely refuse to follow your instructions to cut off your arm. (If you are insistent, you can probably find someone in the body modification community to do it for you, though a) it's probably illegal for them to do so and b) don't confuse that with legitimate medical intervention.)
Lawyers may not be free to do so, though they can try.
In reality there is usually wriggle room concerning motive or the suitability of the charge, say. But I know a lawyer who has turned away clients who have flat out confessed to him.
But how does he know his client is guilty? Is he supposed to judge his client?
What reason would the attorney have for not believing the information that the client confesses voluntarily under the veil of attorney-client privilege?.
Considering the historical reliability of the ways in which we find people guilty of crimes that sounds like a terrible system.
1) Defendants have the right to a trial, regardless of how "obviously guilty" they are in anyone's eyes.
2) Trials are, in part, about whether the state has met its burden to prove the elements of the case, regardless of the lay truth of the accused's guilt. [A]
3) Given the above, the work of a lawyer (in a trial) does not inherently involve the representation that "this defendant is innocent", but only that "there is insufficient evidence of that element of the case", which needn't be a fraud on the court, even if the prosecution's claim is true.
(With that said, more specific lies can be off limits.)
[A] A Man for All Seasons: "The world must judge according to its wits; this court must judge according to the law."
2) Yes.
3) Yes. The difficulty arises when the lawyer has been provided with evidence by the client which supports the charge.
Ultimately it's the lawyers job to present the client's case, however implausible. However, "I did it but I want to pretend I didn't" isn't a case, it's a lie.
If you agree, that's walking back on your original comment; if you disagree, that seems to go sharply against 1/2/3.
Edit: As the others note, this is going sharply against well-known legal principles. Do you have any authoritative citation that UK lawyers can't represent clients at all on a not-guilty plea while believing them to have "done it"?
Edit: the first was, the second was hired by the family, who filed that his client was indigent and he was to be paid from public defense monies.
> But he was continually at odds with his public defenders, eventually firing them for refusing to file subpoenas he prepared for a dozen witnesses, who he said could support his alibi defense and other claims. He briefly acted as his own lawyer until his parents hired Larry English to defend him, and even then, the defendant continued to file motions in his own defense.
> English repeatedly advised McCoy to plead guilty in exchange for life in prison instead of the death penalty or to plead not guilty by reason of insanity, but McCoy repeatedly refused, insisting that he was innocent.
This is how innocent people end up on death row.
A lawyer advising you to plea guilty is not necessarily assuming you are guilty any more than a lawyer saying that you have a solid basis for a not guilty plea necessarily assumes you are factually not guilty.
The lawyer is advising you on their opinion of where you will get the best (which may merely be “least terrible”) result from the legal system.
Now, they may or may not be doing a decent job of that, but that's a different issue.
As a side note, I've been told that public defenders will actually tend to get better deals from prosecutors than private counsel because they have to work together so much that they tend to know when the prosecutor will bend.
Also, I do not condone plea bargaining. I think it generally distorts justice in ways that are very corrupt, and create very mis-aligned incentives.