Kazakhmys's business may be mining - it is one of the world's biggest copper producers - but it might just as easily be categorised as a natural resources investment trust.

The highlight of yesterday's full-year results came not in the Kazakh company's earnings or production figures - flooding and equipment shortages meant that total copper production fell 6 per cent last year - but in the surge in value of its stake in Eurasian Natural Resources Corporation (ENRC).

Its 14.6 per cent interest in the £14billion iron ore and aluminium producer - which is scheduled to join the FTSE 100 this month after its stock market debut in December - is worth $4.2 billion (£2.1 billion), more than five times what Kazakhmys paid for it only five months ago.

With index promotion set to fuel demand for ENRC shares over the next few months - it has a free float of only 21 per cent - Kazakhmys should find no shortage of buyers should it seek to sell when the company's post-float lock-up expires in June.

That massive appreciation helps to offset the fact that Kazakhmys's two most eagerly awaited projects, Boschekul and Aktogay, remain several years away from producing their first copper - late 2011, in the case of the former.

That hiatus also explains why Kazakhmys has been active on other fronts. Last month it paid $1.1billion for the Ekibastuz power station, which makes it the biggest power generator in Kazakhstan. Given the strong growth in the Kazakh electricity market, which should continue, that move appears sound.

Kazakhmys has also made forays into goldmining - as distinct from the gold that it produces as a by-product of copper - and oil exploration, where it has a four-year licence over the Eastern Akzhar block east of the Caspian.

At £17.05, or less than six times 2008 earnings once the value of ENRC is stripped out, Kazakhmys remains the world's cheapest large-cap pure copper play, a status partly explained by the perceived political risk of its home turf, where the Government has a record of scrapping natural resources contracts.

However, it is the 31 per cent rise in copper prices since the start of this year - which, combined with ENRC, has helped Kazakhmys up 64 per cent from its January low - that instils caution.

On the assumption that a weakening US economy makes that rally unsustainable, short-term investors should take profits.

Inmarsat

It is too early to tell whether yesterday's 5 per cent slide in the shares of Inmarsat will be enough to deny it promotion to the FTSE 100 in next week's quarterly index reshuffle. But the £2.2billion satellite operator, floated three years ago, is not the sort of company to covet the limelight. It has no obvious peer group on the London stock market, the long-term nature of its development programmes make it difficult to value, and its numbers are complicated by the depreciation of old satellites and expenditure on new ones.

It was Inmarsat's forecast of a $430million spend this year on development and launches - the third and final of its Inmarsat IV series will enter orbit next month - that partly caught the City on the hop yesterday and unsettled the shares, down 25p at 466p. But Inmarsat has much to commend it. About 60 per cent of sales are drawn from shipping, where the company has benefited from the surge in seaborne traffic that has accompanied globalisation and a move to crews more dependent on high-tech navigation systems. It has also prospered from the extension of oil and gas exploration into regions without terrestrial communications.

That exposure, together with the fact that government accounts for 40per cent of revenues, largely through the military, provide an element of defensiveness. In the meantime, it is rolling out GSM technology for use by aircraft passengers, while its broadband satellite internet telephony is seeing a strong take-up. Stakebuilding by Harbinger Capital, the US hedge fund that holds 28 per cent, provides speculative interest but given a recent strong run, there will be better times to buy. Pass.

Arena Leisure

Last summer, when torrential rain caused the cancellation of a record number of race meetings, was not a total washout for Arena Leisure. As yesterday's full-year results show, the biggest single contributor to the racecourse operator's 7 per cent rise in pre-tax profits was a £6.6 million insurance claim for the flooding of Southwell.

So if the shares dipped modestly, that had more to do with Arena's admission of a slower start to 2008. With an average spend of £25 at its tracks, Arena is vulnerable to both consumer weakness and City job losses: Windsor, helped by Monday evening summer meetings, is one of its two most profitable courses.

But that risk should not be overstated: January and February account for only 8 per cent of annual attendance income. More important is a return to more normal weather patterns between May and September, when Arena expects to book two thirds of income.

Arena cannot be valued on profits alone. Given the scope to redevelop surplus land around Lingfield and Folkestone, it is more akin to a property stock. Last year's receipt of planning permission for hotel and residential schemes at Doncaster, Lingfield and Wolverhampton was encouraging, as was the disclosure yesterday of £39 million of new bank facilities. Although at 52p, the shares lack a short-term catalyst to send them higher, the presence on the share register of Trevor Hemmings and, it is rumoured, the Reuben brothers should provide a floor. Hold.

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