In what many in the stock market saw as a bungled announcement, a company called GIH said it now held a 6 per cent interest in Hogg.
GIH is a subsidiary of HSBC, the Hong Kong & Shanghai Banking Corporation, which owns Midland Bank.
In the normal course of its investment activities HSBC registers an almost continuous stream of shareholdings.
But GIH is not the vehicle for such an exercise. It is the insurance broking arm of HSBC. And takeover alarm bells sounded at Hogg as soon as it became known that its shareholding had stretched from below 3 per cent to 6 per cent.
Anthony Howland Jackson, Hogg's chairman, said: 'We can only presume they have bought them for some predatory reason. We have had no talks with them.'
Hogg took the unusual step of accompanying the announcement of the stake with the traditional advice in suspected bid situations: 'Shareholders are advised to take no action until a further announcement is made by the company'.
HSBC has carefully picked its time to ruffle Hogg. In January the broker forecast lower profits and said it would have to reduce its year's dividend from 8.15p to 5.65p.
Hogg shares climbed 24p to 165p.
The rest of the stock market followed its increasingly familiar roller-coaster track. With New York suffering its biggest fall of the year on Wednesday the market was obviously destined for a bumpy opening. At one time the FT-SE 100 index was down 30.5 points but some bear covering and soothing words from Kenneth Clarke, the Chancellor, had helped the index to a modest gain by mid-afternoon.
Bargain buying dried up when it became apparent that New York had not recovered from its Wednesday jitters and it would be advisable to remain passive ahead of what could be a fraught long holiday weekend.
By the close the 100 index was down 6 points at 3,086.4.
Nicholas Knight, the Nomura strategist once regarded as the arch bull, was another inhibiting influence. He has already cut his 100 index forecast for the year-end from 4,000 to 3,500. His latest contribution was to suggest that the 100 index could hit 2,800 by the end of this month. He is also exceedingly bearish on New York and Hong Kong.
Ian Harnett at Societe Generale Strauss Turnbull also believes there is a considerable downside; he suggests it could go to 2,850. But he looks for up to 3,600 for June and 3,500 for the year-end.
Government stocks made a firm early impression but became weighed down by overseas bond movements and closed with modest gains.
The surprise Capital Radio bid for Southern Radio enlivened broadcasting shares; Southern jumped 25p to 118p and Capital 21p to 418p. Chiltern rose 11p to 163p and GWR 37p to 895p.
But Pearson's pounds 312m capture of a US software group was poorly received, leaving the shares 26p lower at 641p.
The new issue pack met a mixed response. Groupe Chez Gerard, the restaurant chain placed at 112.5p, ended at 112p but Trafficmaster reached 149p against a 130p sale price.
The undoubted star of the bunch was Unipalm, a software group, which surged to 136p from a 100p placing. For Maid, one of the more controversial new issues of the current recruits, it was a poor session. The shares, which have yet to reach their 110p offer price, fell 14p to 87p.
Capital Shopping Centres, where sponsor Robert Fleming Securities stands by to offer support, fell a further 2p to 206p. The offer price was 230p.
Two returned to the listing fray. Embassy Property, suspended at 3p, came back at 1.25p and United Industries, halted at 17.5p, returned at 15p.
Both groups have been transformed. Embassy put through acquisitions in Britain and China and UI acquired three engineering groups for pounds 25m from its 20 per cent shareholder, BBA. Now run by Tom Brown, ex-Fenner, it hopes to return to the dividend list this year.
Redland, with a 40 per cent profit increase, achieved a 15p gain to 539p and the builder Taylor Woodrow put on 5p to 159p. RMC recovered most of an early loss on the roadbuilding cutback to close 2p lower at 936p.
The revamping exercise at Andaman Resources, unchanged at 17p, got under way with the purchase of Southern Roadmaking and 24.9 per cent of Fleet International. To help the deal, the stockbroker Charles Stanley is placing 3.7 million shares.
Atreus, the shower screen group that made a profit warning in January, held at 16p as Gerry Ceclich resigned as finance director.
Another volatile session left the FT-SE 100 index down 6 points at 3,086.4 and the FT-SE 250 index lost 14.2 to 3,752.9. Turnover was 725.6 million shares with 40,901 deals. The account ends on Friday with settlement on 18 April.
Aminex, the Irish group that has led the oil pack into the former Soviet Union, is thought to be near to clinching a deal that will expand its operations sharply. It has established close links with Russia and a leading Russian group has an indirect 40 per cent interest in Aminex. Its shares, 4p at the start of last year, have topped 100p. Yesterday they closed at 62p.
Europe Energy's drive from a Welsh mining group to motor dealer is under way. It has agreed to buy a Finchley, London, Rover dealership from Inchcape. The pounds 1.2m cost is being met in cash and a share placing. More deals are expected. Gerald Davison, former Keep Trust chairman, moved in last year and there has since been a pounds 1.8m cash call. The shares are 14.5p.