Top-flight shares are on track for a record 14th consecutive day of gains buoyed by bid talk over ITV.
The FTSE 100 Index lifted 30.1 points to 7,322.4 in afternoon trading, after last night also posting a record 11th day in a row of closing highs. The FTSE 250 Index rose 50 points to 18,353.4.
Broadcaster ITV was also in high demand on hopes of merger activity, fuelled by a note from Goldman Sachs. Traders are well aware that US media giant Liberty Global, which owns Virgin Media in the UK, has signalled its desire to make acquisitions.
Shares in ITV, regularly mentioned as a takeover target, rose 6p to 209p.
CMC Markets chief market analyst Michael Hewson said: "ITV is higher as speculation about its mergers and acquisition potential once again prompts some speculative buying."
Over recent weeks the market has been driven by hopes of the $1trn (£818m, €936m) infrastructure package promised by US President-elect Donald Trump.
A second factor is the weakness of the pound against a basket of major currencies since June's Brexit vote. Footsie shares are more appealing to investors when the pound falls because most of these firm's sales are earned aboard, boosting revenues when translated back into sterling.
The biggest risers in the FTSE 100 Index were Barratt Developments (+16p to 514p), ITV (+6p to 209p), Kingfisher (+9.6p to 353.8p), International Airlines Group (+11.1p to 490.3p) and St James's Place (+23p to 1,082p).
The biggest fallers in the FTSE 100 Index were Rolls-Royce (-11.5p to 665.5p), Marks & Spencer (-4.8p to 340.1p), Paddy Power Betfair (-80p to 8,660p), BAE Systems (-5p to 612.5p) and Fresnillo (-11p to 1,411p).
The biggest risers in the FTSE 250 Index were SIG (+16.1p to 110p), Grafton Group (+41p to 581.5p), International Personal Finance (+9.3p to 173.1p), Daejan Holdings (+165p to 6,165p) and Travis Perkins (+35p to 1457p).
The biggest fallers in the FTSE 250 Index were Dunelm Group (-48p to 694p), Pennon Group (-36.5p to 772.5p), Euromoney (-49p to1126p), AO World (-6.1p to156.2p) and Evraz (-7.1p to221.1p).