This article was adapted from our sister site across the pond,  Fool U.K.

At the end of 2010, there were 2,289 securities listed on the main market of the London Stock Exchange and the Alternative Investment Market (the LSE's junior market).

U.K. in a nutshell
However, this figure includes hundreds of international firms with secondary listings. Stripping these out, there are 1,961 U.K.-incorporated companies with ordinary shares listed on the LSE or AIM. In total, these companies have a combined market capitalization approaching 2 trillion pounds.

Of course, each company doesn't have the same impact in investment terms, because the U.K. market is made up of "a few giants and a parade of midgets." For instance, at the lower end of this scale, 1,063 of these firms have a market value of under 50 million pounds, putting them firmly in the "micro-cap" category.

At the other end of this spectrum are the giants: those few British companies that truly have a massive impact on world capitalism. Each is a household name in its own right, and all loom large on the global stage.

10 global Goliaths
Let's look at the largest of these listed Leviathans -- the 10 largest companies in the U.K. stock market:

Company

Market Cap
(in pounds)

P/E Ratio

Dividend
Yield
(%)

Royal Dutch Shell (NYSE: RDS-B) 134 billion 21.3 4.9
HSBC Holdings (NYSE: HBC) 126 billion 33.3 3.0
BP (NYSE: BP) 96 billion 9.2 6.9
Vodafone Group (NYSE: VOD) 93 billion 11.1 4.7
Rio Tinto (NYSE: RIO) 68 billion 19.9 0.6
GlaxoSmithKline (NYSE: GSK) 61 billion 9.7 5.2
BHP Billiton (NYSE: BHP) 55 billion 17.8 2.2
British American Tobacco (AMEX: BTI) 47 billion 15.4 4.2
BG Group  46 billion 20.3 0.9
Lloyds Banking Group (NYSE: LYG) 46 billion 9.0 -

Source: Digital Look. In pounds, not dollars.

As you can see, top of the heap is oil giant Royal Dutch Shell, weighing in with a market cap of 134 billion pounds. Next come megabank HSBC and battered BP (whose value plummeted in 2010, thanks to its Gulf of Mexico oil spill).

Vodafone enters our chart at No. 4. In just 26 years, a small Berkshire-based mobile-telephone business has been transformed into a global brand, with 343 million customers in 70 countries. In fifth and sixth places are Rio Tinto, one of the world's largest miners of aluminium, copper and iron ore, and then GlaxoSmithKline, the world's fourth-largest drug manufacturer.

Completing our set are miner BHP Billiton, cigarette maker British American Tobacco, natural gas producer BG, and Lloyds Banking Group (now 41%-owned by U.K. taxpayers).

B-I-G businesses
Our list of the 10 biggest U.K.-listed companies has some diversification, being spread across two banks, two miners and two oil firms, plus one each in the energy, pharmaceutical, telecoms, and tobacco sectors.

What more, this portfolio of giants has a strong global reach, as each of these firms is of international importance. In fact, with the notable exception of Lloyds, the vast majority of these companies' earnings come from outside the U.K.

The total valuation of the FTSE 100 is just short of 1.7 trillion pounds, so these companies account for almost half (46%) of the entire Footsie. In other words, these 10 firms dominate and drive the performance of the blue-chip index (which itself makes up 85% of the entire U.K. stock market). Truly they are the British titans!

The picks of this pack
Personally, I'd be fairly happy to have a substantial holding in any of these companies, as each enjoys an enduring competitive moat, thanks to their huge customer bases, commanding market shares, and powerful brands.

In addition, these giants lie at the core of countless investment funds and private portfolios, making them the most-watched companies in the investment universe. 

However, with my value-investing hat on, my favored shares from this list would have to be Glaxo and Vodafone. Both are modestly rated, at 9.7 and 11.1 times earnings respectively. What's more, both pay much higher dividends than the market average.

Also, both firms have strong balance sheets and throw off billions of pounds in free cash each year -- money that can be earmarked for acquisitions, share buybacks, and increasing dividends. Lastly, the shares of each of these 10 firms are highly liquid, which makes for easy buying and selling, with tiny bid-offer spreads even when dealing in bulk.

What more could you ask for in a company? What are your views on these 10 titans of British business? Please let me know in the comments box below ...

More from Cliff D'Arcy:

Cliff owns shares in GSK. Vodafone Group is a Motley Fool Inside Value choice. GlaxoSmithKline is a Motley Fool Global Gains recommendation. The Fool owns shares of and has written covered calls on GlaxoSmithKline. The Motley Fool has a disclosure policy.