A competitor:

David Phillips - former Hackney Councillor

Elected as Labour - 1994
Expelled/Defects to "Hackney New Labour" when group splits - 1996
Defects to Conservative 1997
Re-elected as Conservative 1998
Expelled by Conservatives 1999 ish
Sits as Independent
Later joins Green Group on council but takes out national party membership of Lib Dems
Defeated as Green candidate 2002
Defeated as Lib Dem candidate 2006

Oh what a pity, those couple of defeats take the shine off David Phillips' achievements!

There are other challengers.

Pat Knight, who was a Croydon councillor in Fairfield ward 1998-2006 has a claim. John Cartwright, of the Croydon Monster Raving Loony Party, notes her career as follows:

"1998 elected as Conservative
2002 May: re-elected as Conservative
2002 July: joined Labour
2003 (early): re-joined Conservatives
2004 April: resigned from Conservative group and became independent
(I think she applied to re-join Labour but was refused (I am not certain of this))
2005: Joined Lib Dems and thus made the Lib Dem councillors into a "group" of 2 members
2006: stood in Coulsdon East ward (the only ward in Croydon where the Lib Dems are anywhere near winning) and came third out of the three Lib Dem candidates.

I have been told that in her youth she regularly commuted between the Labour Party, the CPGB and the SDP."

Then there is Herbert Crossman of Harrow. Colin Gray describes his trajectory:

"Elected as a Lib Dem councillor for Ridgeway ward in 1994. Resigned from the Lib Dems in August 1995 and announced he would sit as an Independent. In September 1996 he became PPC for the Referendum Party in Harrow West. In November 1997 Crossman formed "The Constituents' Party" with another Independent councillor, but this grouping dissolved in March 1998 when Crossman joined the Conservative Party. Unsuccessful Conservative candidate in May 1998 for Rayners Lane ward. In February 2002 he formed yet another local "party", the "People's Independent Party" (PIP) who fielded a number of candidates at both the 2002 and 2006 elections. Makes a reappearance at this by-election as an Independent. Known locally as Herbie '5 Parties' Crossman."

There is Tim Perkins of Salford, who went:

Labour
SDP
Lib Dem
Conservative
Pro European Conservative
Lib Dem again
Progressive Conservative
Conservative again

And then Dave Barnes of Islington:

Elected first as Labour
Went Independent
Joined Lib Dems
Went Independent
Joint Local Justice For Islington Residents (pro parking) party
Joined Conservatives
Lost seat

Looks like he's now moving towards UKIP. His history in the Church follows a similar pattern."

In my mind there is only one contender in my lifetime - David Owen - without him and his muppet followers we may have been spared a few more years of the Thatcherites. He also spread his poison to former Yugoslavia in latter years. Last seen writing a book about how power affects the minds of prime ministers - without appreciating the irony that the minds of failed politicians may be even more adversely affected.