The two banks have extensive Pacific connections and their shares, in busy trading, encountered determined selling.
HCBC sterling-denominated shares slumped 150.5p to 1,960.5p and Standard 103.5p to 874p.
After their rip-roaring run the two banks are clearly vulnerable to any tidings of woe and they were unable to withstand the wild stories flying around about likely developments in the Far East.
Only weeks ago the market was awash with heady forecasts about HSBC, owner of Midland Bank, and Standard. Analysts were convinced they would move higher with, for example, some advocating that HSBC would soon hit 2,600p. It did, earlier this month, achieve 2,347p but has since drifted lower.
The Far Eastern upheaval has caught the market on the hop. Thailand's well-documented problems were seen as an isolated, one-off problem; not one which could engulf other nations.
Standard had already weathered the Thailand financial crisis. Last month it was hit briefly by worries it had sustained heavy derivative losses following the slide in the country's once booming currency, the baht.
The Malaysian ringgit is the latest casualty, hitting a new low for the second day running. Indonesia's rupiah, the Singapore dollar and the Philippine peso were others under pressure.
There are fears the raiding speculators will soon turn their attention to the Hong Kong dollar. The overnight 657-point fall to 1,4876.1 in the Hang Seng share index was, however, dismissed as a technical setback by some London traders. The success of the latest Hong Kong land auction, they suggested, showed the former colony's economic health was too robust for its currency to wilt under pressure. And the Chinese authorities were in a strong enough position to, if necessary, counter any raid.
The rapidly expanding Far East has provided a happy hunting ground for many companies and the impact of the Pacific storm was not confined to the two banks. Cable & Wireless, suffering the added distress of a loss by its Australian associate, had to wrestle with its Hong Kong Telecom involvement, falling 18.5p to 543p.
Inchcape, with extensive Pacific interests, lost 13.5p to 271.5p and luxury goods group Vendome fell 14.5p to 461p. Far Eastern investment trusts suffered the predictable pressure.
Footsie fell 61.5 points to 4,845.4 with New York combining with the Far East to inflict a double whammy. US investors were again fretting about interest rates and the Dow Jones was sharply lower in London trading.
The raft of company results was largely encouraging. Still, squeezed margins and Far Eastern exposure put Rolls-Royce into a spin, off 19p to 235.5p in heavy trading. Reckitt & Colman was another weaker, 20.5p to 961p, after results.
Heavy trading in Great Universal Stores lowered the price 12p to 633p and Vodafone fell 4.5p to 309.5p despite upgrades following better-than- expected subscriber figures.
BT shaded to 402p with arbitrageur-inspired trading lifting Seaq turnover to nearly 85 million shares.
Telewest, the country's second-largest cable group, fell 4p to 75p although it denied merger talks, thought to be with NTL, had collapsed.
Scottish & Newcastle hardened to 724.5p on its trading statement and Allied Domecq added 5.5p to 466p as NatWest Securities said it was a "weak hold". Ladbroke, on results, firmed 1p to 261.5p.
Thistle Hotels, encouraged by Ladbroke's hotel returns, gained 10.5p to 153p.
Commercial Union resisted the downward pressure, gaining 11p to 745.5p, just below its year's peak, as takeover hopes stirred again. Norwich Union, on Halifax bid speculation, was at one time up 5p at 350.5p but ended 6p lower to 339.5p. Schroders, the investment group, edged ahead 17.5p to 1,882.5p. The market remains convinced a mega-bid in the financial sector is being prepared.
Leigh Interests, the waste disposal group on the end of an agreed 175p offer from General Utilities, the French group, rose 21p to 173p.
Anglesey Mining, struggling to reactivate mining on Parys Mountain in North Anglesey, rose 1p to 3.75p, reflecting a share placing at 5p.Reuse content