We had a timely warning on the risks of the volatile Alternative Investment Market last week when a dire performance from satellite communications group Avanti took the edge off another strong showing by the majority of our share tips.

Avanti's shares were added to our 2012 portfolio at the start of the week in the belief they had hit rock bottom after an earlier profit warning, but our confidence took a knock as the shares plunged another 8% in the following days.

Followers claim there has been relatively little selling and still expect an early bounce after a 60% fall in the share price over the past year, pointing out that the group's net assets are now worth £100 million more than its stock-market value. Others fret about a lack of comment from the company's directors during the latest share price slide.

We are hoping for the best but will sell our notional holding if the shares slip to our stop/loss level.

The Avanti performance cancelled out gains elsewhere in the 2012 portfolio, which ended the week with a fractional loss.

Our other portfolios all recorded further gains over the week, with our latest 2013 selections passing the 25% profits level for the first time and the 2010 list making further progress towards regaining the 100% appreciation level reached at the end of May.

Six of our recommendations hit new 2013 highs during the week, including Stagecoach, British Polythene Industries, brewery Fuller Smith & Turner, residential landlord Grainger, and heavyweights Centrica and Legal & General.

We have raised our stop/loss levels on each of the shares to ensure we can lock in the bulk of recent profits on any major setback.

This figure is set 10% below the highest price recorded by individual shares; we use it as a signal that the investment has passed its peak.