The shares have been in ragged retreat for the past year. A year ago they were riding high at 663p. Then the premium rating began to disappear.
Mildly disappointing interim figures piled on the agony, prompting some analysts to pull back their year's forecasts to around pounds 105m, against the pounds 96.1m produced last time.
The group is a casualty of sterling's strength. But with its catalytic converter in the fashionable area of reducing exhaust emissions and hopes riding high for its electronics materials business, Johnson's fall from grace has surprised some observers.
Year's figures are due soon and the sinking shares suggest acute disappointment is on the horizon.
Footsie ended up 19.8 points at 4,681.6 just 12.3 points off its closing peak. In relatively thin trading financials were again the pace setters as the market continued to anticipate the arrival of Halifax next week and later this month Norwich Union. Financials filled the top seven places on the blue-chip leader board with insurance group Legal & General to the fore with an 18p gain to 481p.
Abbey ended 12p higher at 944.5p after touching 950p and Alliance & Leicester seesawed from a 13p gain to end with a 10.5p fall at 627.5p.
National Westminster Bank missed out, falling 5.5p to 785.5p over worries about a reported link with City Mortgage Corporation, a US lender under investigation. Sun Life & Provincial, said to be eyeing Equity & Law, gave up 8.5p to 314.5p.
Zeneca was another to experience a topsy-turvy day as Roche, the Swiss group, took over a German operation, seemingly ruling out the long rumoured strike at the drugs group. At one time down 31p, the shares rallied to close just 2p lower at 1,876.5p with many of the supporters of the takeover story content to exchange Roche for Glaxo Wellcome as the rumoured predator.
The surprise swing in the French elections was seen as reducing the likelihood of any significant British involvement in the French defence industry, lowering British Aerospace 15p to 1,239.5p and General Electric Co 4p to 354p. Rolls-Royce dived 8p to 242.5p as the Cathay Pacific airline grounded its A330-300 fleet because of problems with its Rolls Trent 700 engines. British Airways, said to be in talks to buy Alitalia, fell 14.5p to 711p.
Some football shares had that "sick as a parrot" look. Sheffield Utd's failure to clinch promotion to the Premiership prompted a 20p fall to 45p; the price topped 100p in February and Southampton's managerial vacuum lowered the shares 11p to 91.5p (against a 151.5p peak). Silver Shield, the windscreen franchise group, put on 0.75p to 3.5p on talk it was planning a deal involving Swansea City.
Imperial Chemical Industries firmed 4.5p to 798.5p as Salomon Brothers suggested a 12-month target of 900p but BTR, the hard-pressed conglomerate, had another uncomfortable session, falling 8p to 209p, a 12 month low.
Boots, reported to be planning a pounds 400m share buy-back or special dividend, added 12p to 725p. A signalled share buy back at EMI failed to overcome disappointing figures and the shares finished 48.5p down at 1,172.5p.
BBA, the engineering group, came in for a speculative run, ending 8.5p higher at 329.5p; American Port Services was another said to be on a predator's strike list, gaining 10p to 162.6p.
Shell jumped 20p to 1,209.5p, largely on hopes any Government tinkering with ACT would not hit its dividends because of the need to retain the payment relationship with the group's Dutch side. Among the oil tiddlers Emerald Energy confirmed it had been awarded extra exploration acreage in Colombia. The shares firmed 0.25p to 5.25p.
Celltech's sceptic shock drug disappointment continued to weigh on the shares, off 13.5p to 334p. Interim figures are due today. Cortecs International put on 4.5p to 217p as Nomura said buy with analyst Nick Woolf producing a 420p target.
The Savoy Hotel low-voting "A" shares stretched 15p to a 1,597.5p as speculation continued that Granada was near to clinching a deal with the Wontner family which controls the group through the powerful "B" shares.
A favourable trading statement lifted watch maker Dailywin 11p to 79.5p.