Liberal Democrats celebrated a gain in the latest council by-elections from Tories who, however, defended two other marginal seats and control of South Cambridgeshire District.
Andrew Bannerman triumphed for Lib Dems at Quarry and Coton Hill, Shropshire despite a strong intervention by Labour which did not fight last time.
But, at South Cambridgeshire, Tories easily held on at Bourn to keep their council majority of one.
There was also relief for Conservatives when they defended a Kenton seat at north London's Brent Borough.
The ward, a Tory stronghold since the council was created in 1964, had slipped into the marginal category in last May's main polls.
Brent London Borough - Kenton: C 1063, Lab 907, Ind 185, Lib Dem 179, Green 75. (May 2010 - Three seats C 2805, 2667, 2333, Lab 2218, 1832, 1799, Lib Dem 1013, 782, 630, Green 287, 265, 230). C hold. Swing 2.6% C to Lab.
Shropshire County - Quarry and Coton Hill: Lib Dem 356, C 268, Lab 197, Ind 30. (June 2009 - C426, Lib Dem 353, Green 141, Albion Party 57). Lib Dem gain from C. Swing 8.9% C to Lib Dem.
South Cambridgeshire District - Bourn: C 874, Lib Dem 345, Lab 337. (May 2010 - C 1935, Lib Dem 1670, Lab 489, Ukip 180). C hold. Swing 13.9% Lib Dem to C.