Mrs Parkin, hitherto the party's 'greatest asset', was ejected from its leadership. Mr Icke, whose self-declared Messianism made him arguably one of its greatest liabilities, was greeted with enthusiasm. Both responses seemed proof of a collective death wish.
Many leading environmentalists will shed few tears for the Greens, believing them to have been a fractious irrelevance to the cause. But is the Green Party in abrupt terminal decline? And if it dies, will green politics die with it?
Tom Burke, former chairman of the Green Alliance and now a special adviser to the Government, is among those who believe that the Greens had their opportunity - the surge of support which saw them claim 15 per cent in the 1989 Euro- elections - and fluffed it.
Yet the green movement itself is one of the most spectacular growth stories of the last decade. Unofficial estimates put the membership of environmental groups at about 5 million (Labour Party membership is 261,000). The Green vote at the April general election was 170,000 - 1.3 per cent. Why the mismatch?
In the UK, in contrast to much of Europe, the Greens face an electoral system that penalizes minority parties. Government and bureaucracy are strong, Parliament weak. Those pushing for a green agenda have found more influence within pressure groups - Greenpeace, Friends of the Earth - than a minority party.
Many senior figures in the party believe the pressure groups have let it down by withholding their support. Robin Grove-White, director of the Centre for the Study of Environmental Change at Lancaster University and a former leading environmentalist, describes the suggestion as 'quite extraordinarily facile'.
Identifying with the Green Party would have meant voluntary groups losing charitable status and being frozen out by the main parties, he says.
'Environmental politics is about enormous tensions in industrial society - not just technological problems but values, processes and structure. These are not being adequately addressed by the dominant political parties. There is a need for something major and new.'
Should Green Party supporters give up politics and return, in Mr Burke's words, to 'lives of quiet desperation'? Or should the party tough out the political winter ahead?
Peter Wilkinson, former UK chairman of Greenpeace and now an environmental consultant, describes the party as a 'critical element of the green movement. It is its political wing. Given that the party hasn't a hope in hell of running the country for the foreseeable future, the real priority is to influence the mainstream parties' policies. But there has to be a ginger group - a political organisation like the Green Party.'
If the greening of the political agenda is the criterion, then the Greens have already achieved some success. Indeed, a Mori poll commissioned by WBMG, Mr Wilkinson's consultancy, last week showed that most MPs would support radical green proposals. Yet, if the green tide is lapping through industry, society and even into Parliament, the Government holds out against it. According to Mr Wilkinson, this makes electoral 'success' marginal - what difference would a few Green MPs make?
Green Party members apparently agree. According to a Strathclyde University survey, half of them are reconciled to the novel idea of the party as an electoral pressure group whose main job is to influence the other parties. Most members, particularly activists, are prepared for a long haul and do not define success in electoral terms.
Even critics of the Greens, such as Mr Burke, believe that the public will continue to look for a 'green political choice'. Green Party activists - those, at least, who are staying - see their job as to refine this and elaborate so-called 'fundamentalist' policies on issues such as population and economic growth. The alternative is to pronounce the system incapable of reform and turn, as Mr Icke has done, to spiritual reformation.
The Strathclyde survey indicates that the Green voter is younger, better educated and more 'post-materialist' than the average, and fed up with the main parties. A fortnight before the British Green vote collapsed in April, the French Greens were registering 14 per cent in regional elections. Both the British and European experience suggest that the Greens are not a 'flash' party but an enduring phenomenon, waxing and waning according to the public mood. The Greens may be in retreat, but they will probably return.