Hi Paul & Ian,
It was stated that it was a pot of tea - presumably near boiling hot.
The most that we can expect to achieve on a wool carpet without causing consequential damage, is to remove the surface staining.
As I stated in my earlier reply, at this sort of temperature some of the staining elements of the tea would have entered the dye-sites that had been opened by the heat and blended with the original fibre dye. The amount of liquid involved means that the fibres were kept at the elevated temperature for long enough for this process to be completed to an advanced degree.
I would agree with Woodman on the improvement issue, but since a fairly high proportion of the stain would be unreachable, in this instance it would take a lot to persuade me to proceed. Custards sometimes will encourage an attempt, then come back with "I thought it would look better than that)
If an insurance company requested the attempt, against my advice, that would be a slightly different matter in that the chances of shifting the liability to me (provided the attempt was to a professional level) would be removed.
John.