"Given the sudden breakdowns in the charts of Tesco and Carnival on the news affecting them in the last few days, does this offer a buying opportunity - based on technical analysis - for two very strong companies?"

David Fuller's view Thanks for an interesting question which Eoin and I found ourselves discussing from several standpoints.

Both Tesco (weekly & daily) and Carnival (weekly & daily) were underperforming the UK FTSE 100 Index before the latest news which led to sharp corrections. These setbacks would be less meaningful individually if the entire market had fallen but this was not the case so there are now legitimate questions over the medium-term outlook for both companies.

For instance, does Carnival have only one irresponsible captain (hopefully) or is there a lax culture in the firm (hopefully not)? Meanwhile, the company now has an image problem which will not be erased overnight. Tesco's disappointing results in an exceptionally competitive industry which it used to dominate may be an even more serious problem. How long will it take them to turn this around, especially as they are reliant on the UK for 65% of their revenue and the small US unit remains a loss leader?

Nevertheless, from an investment perspective Fullermoney has long favoured buy-low-sell-high. Technically, one can say that both Tesco and Carnival now look overextended following their sharp declines. They are also approaching areas of previous support. Both have attractive yields of 5.25% and 3.81%, respectively, which should be secure for at least the medium term.

Tactically, does a prospective buyer now nibble on easing or wait for some evidence that these shares are finding support? If the whole market had fallen I would prefer to see some evidence of relative strength but under the circumstances we may not see that until both shares are well off their lows.

Bottom line: if you were thinking of buying Tesco and Carnival shares before the recent declines and feel that their problems are likely to be temporary, I would now nibble on easing. You will probably have to be patient but the consolation is the higher yield.