Labour are still not able to get voters away from the Conservatives...
A slight increase in their numbers and the Conservatives could get 50% or more of the voters, which would be the first time any party has managed to do that since the Conservatives in 1931 (55.5%).
The last three times any parties got votes in the high 40s were Conservatives in 1955 (49.7%) and 1959 (49.4%), and Labour in 1966 (48%). The best Thatcher achieved was 43.9% in 1979, Blair managed a similar figure of 43.3% in his best win, 1997.
The biggest post-war margin of victory is 1983, when Thatcher's Conservatives had 14.8% more of the vote than the Labour Party led my Michael Foot. The largest I can find is the 24.7% margin of victory enjoyed by the Conservatives in the 1931 election mentioned earlier, I highly doubt May will come close to that.