She rode a much-modified GT 200 built by Filtrate Oils and Lambretta Concessionaires UK.
Marlene, a taxi driver from Bristol UK, was selected from 67 women who applied for the task of piloting the streamlined scooter to a speed in excess of 110 mph, the current record for the class.
In her form-fitting all-white leathers she took the miniscule 50cc streamliner to 130mph, shattering the record. Or so some reports stated. An Italian article states that Marlene achieved 180 km/h (112mph) but did not take the record, and a BSSO post states that the Lambretta had overheating problems and was "severely trounced" by two Italian teams which each achieved over 100mph.
Forty years later the original machine (called the Atlanta V) was found to still exist at a German specialist scooter shop.
The bike was designed by Robert Forest-Webb of Hertfordshire and the attempt was sponsored by Lambretta Concessionaires UK and Filtrate Oils.
The Lambretta, after some interesting exploits, passed from A. Francis to Mike Karslake, and then went to the Scooter Centre Cologne.
In 2009 Emily Koch of the Bristol Post was involved in a project to find Marlene Parker. As of 2011 there appears to have been no result.
"Red Devil" writes in the BSSO post (below) "Marlene was probably not one of the fastest Lambretta ladies around during the 1960's, I can name a few others who were fast. Ann Wier, Bev Flanagan and Londoner Christine Jackson who had been riding Lambretta's competitively since her late teens."
Sources: scooterlounge.com, contemporary reports, thereunion.it, BSSO, et al.