Blue chip shares opened the year in the same record-breaking fashion they closed 2016, by setting a new all-time mid-session high.
The FTSE 100 Index rose 35 points to 7177.7, after earlier hitting a new peak of 7205.2 in early trading as investors on both sides of the Atlantic remain buoyed by the prospect of a $1trn (£814bn) infrastructure spending package by incoming US President Donald Trump. The FTSE 250 lifted 67.3 points to 18144.5.
Top flight shares ended 2016 by hitting a trio of all-time closing highs over the final three days of the year.
UK economic data saw Britain's manufacturing sector hit a two-and-a-half-year high last month, according to a survey.
The Markit/CIPS purchasing managers' index for the sector rose to 56.1 in December from 53.6 the month before. A figure above 50 indicates expansion.
The weaker pound helped to boost orders from overseas, the survey found, with the sector starting the year on a "strong footing".
IG market analyst Joshua Mahony said: "With the UK's enactment of Article 50 likely to spark another leg lower for the pound, there is a good chance that 2017 could prove a positive one for UK exporters."
In afternoon trading the biggest risers in the FTSE 100 Index were Barclays (+7.8p to 231.2p), Hargreaves Lansdown (+40p to 1253p), Lloyds Banking Group (+1.9p to 64.4p), Glencore (+8p to 285.4p) and Royal Bank of Scotland Group (+6p to 230.5p).
The biggest fallers in the FTSE 100 Index were Next (-165p to 4818p), Dixons Carphone (-8.6p to 346p), Marks & Spencer (-7.1p to 343p), CRH (-47p to 2783p) and Micro Focus International (-36p to 2143p).
In afternoon trading the biggest risers in the FTSE 250 Index were Tullow Oil (+17.2p to 330p), Metro Bank (+125p to 3050p), Weir Group (+74p to 1964p), Aldermore Group (+8.8p to 245.6p) and Aberdeen Asset Management (+8.5p to 265.8p).
The biggest fallers in the FTSE 250 Index were Halfords Group (-22p to 343.5p), Capital & Counties Properties (-12p to 285.1p), Acacia Mining (-14p to 360p), Countryside Properties (-8p to 240.8p) and N Brown (-6.7p to 215.8p).