The London market lifted in afternoon trading as traders were encouraged by a recovery in the construction sector.
The Markit/CIPS purchasing managers' index for the sector rose to 49.2 in August, but stayed below the 50 level, which indicates contraction. But the data was an improvement on July's figures of 45.9, the lowest for seven years.
Spreadex financial analyst Connor Campbell said this survey and other recent reports "pointed to a less perilous post-Brexit situation than was forecast".
The FTSE 100 Index lifted 72 points to 6,818, buoyed by banking and pharmaceutical heavyweights. The FTSE 250 Index rose 46 points to 17,895.6.
In the second tier, the transport group that runs strike-hit Southern rail said its profits leapt almost 27% to £99.8m ($132.5m) in the year to 2 July, after seeing record rail passengers across its franchises and hitting record earnings at its bus division.
However, Go-Ahead's chief executive David Brown turned down his bonus because of delays and cancellations at its Southern franchise which runs commuter services between London, Surrey, Sussex and Kent.
Investors were cheered, however, by Go-Ahead's jump in profits which saw its shares lift 163p to 2,161p.
In afternoon trading the biggest risers on the FTSE 100 Index were Imperial Brands (+122p to 4,084.5p), Hikma Pharmaceuticals (+60p to 2,138p), Unilever (+86.5p to 3,614p), British American Tobacco (+110p to 4,823.5p) and National Grid (+23.5p to 1,064p).
The biggest fallers on the FTSE 100 Index were Carnival (-147p to 3,519p), Persimmon (-40p to 1,830p), Taylor Wimpey (-3.2p to 162.4p), Berkeley Group Holdings (-52p to 2,723p) and Barratt Developments (-7.3p to 492.7p).
In afternoon trading the biggest risers on the FTSE 250 Index were Go-Ahead Group (+163p to 2,161p), Amec Foster Wheeler (+22p to 566.5p), Acacia Mining (+17.3p to 480.1p), Indivior (+7.8p to 325p) and NMC Health (+33p to 1392p).
The biggest fallers on the FTSE 250 Index were McCarthy & Stone (-22.5p to 187p), Ibstock (-18.2p to 168p), SIG (-4.4p to 122.7p), Intermediate Capital Group (-18p to 591p) and Countrywide (-7.5p to 261.1p).