Today I’m examining the investment prospects of three pressured London giants.

Bank in bother

Financial colossus Standard Chartered (LSE: STAN) has been forced to swallow even further share price weakness since the start of 2016. Fears over emerging market cooling are currently running at fever pitch, fuelling speculation that further heavy impairments and revenue struggles could be on the cards for the Asia-focused bank.

Indeed, ‘StanChart’ stunned the market on Tuesday with news it slumped to its first annual loss since the late 1980s in 2015 — the business swung to a $1.5bn loss from a $4.2bn profit the previous year.

The company has subsequently binned the dividend, and warned that “there remains a broad range of macroeconomic uncertainties and challenges in the global economy, including the rebalancing of China’s economy, the impact of lower commodity prices, and ongoing geopolitical tensions.”

With the London business also in the process of massive restructuring, I believe Standard Chartered remains too risky at the current time, regardless of the long-term opportunities created by its far-flung markets.

And while a projected 28% earnings bounceback for 2016 leaves the bank dealing on a P/E rating of just 10.9 times, I reckon the likely prospect of bottom-line downgrades makes the bank an unappealing selection even at these prices.

Engineer terrific returns

I’m far more optimistic concerning car and plane parts supplier GKN (LSE: GKN) however.

The share has conceded a quarter of its value during the past year as concerns over the fallout of the Volkswagen emissions saga — VW is comfortably GKN’s largest auto customer — as well as signs of slowing civil aeroplane demand have weighed.

Still, I consider this weakness to be a prime buying opportunity. The Redditch firm is a critical supplier to the world’s biggest car- and plane-builders, and shrewd acquisitions like that of Fokker last year further cement GKN’s top-tier status. Besides, there’s no doubt that rising road and air travel in the years ahead should power demand for the manufacturer’s wares.

The number crunchers expect GKN to respond from a predicted 10% earnings decline for 2015 with a 3% bounce this year, resulting in a P/E rating of just 11 times. I reckon this represents stunning value for such a high-quality engineer.

Metals play getting mashed

Although all major commodity classes have recovered from fresh multi-year lows, I believe the prospect of further price weakness makes producers like Rio Tinto (LSE: RIO) a risk too far at present.

The London-based digger has pulled out all the stops to lessen the effect of falling resources prices in recent years. But despite round after round of cost-cutting and capex reductions — not to mention a stream of asset sales — Rio Tinto continues to be battered by huge supply/demand balances across its main markets.

The firm was forced to put its progressive dividend policy on ice this month after announcing a colossal 51% earnings slide in 2015, to $4.5bn. And I expect further bottom-line pain to transpire as China’s economy cools, and production levels across the critical iron ore, copper and aluminium segments rise.

The City expects Rio Tinto to endure a third successive earnings slide in 2016, this time by a chunky 15% and leaving the business dealing on a P/E rating of 14.2 times. I consider this poor value given the worsening state of the firm’s key markets, and expect share prices to keep on slipping.

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Royston Wild has no position in any shares mentioned. The Motley Fool UK owns shares of GKN. The Motley Fool UK has recommended Rio Tinto. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.