Blue chip shares struggled for direction in subdued afternoon trading at the start the week before Christmas.
The FTSE 100 Index lifted 9.2 points to 7,020.8, amid light volumes as the market looked unlikely to match significant strides made last week. The FTSE 250 Index slipped 0.4 points lower to 17,784.4.
IG market analyst Joshua Mahony said: "The week has started in somewhat uninspired fashion, with European indices trading largely sideways as we await the next big move. The festive season typically brings with it diminished volumes and the expectation of higher volatility."
However, Mahony added that despite the Brexit vote, the Italian referendum decision, Donald Trump's election as US president and the Federal Reserve's decision to raise interest rates "markets were holding up remarkably well".
Oil major BP lifted 2.9p to 492.5p, after it said it had struck a deal for just under $1bn (£800m, €950m) to drill for gas in Mauritania and Senegal.
The move follows another $2.2bn deal hammered out by the firm last week to gain access to oil fields in the United Arab Emirates.
Recent deals announced by BP signal that the firm is turning to acquisitions to expand the business after several years of shrinking, as a result of the 2010 Deepwater Horizon oil spill in the Gulf of Mexico, which has cost it more than $60bn.
In afternoon trading the biggest risers in the FTSE 100 Index were Hikma Pharmaceuticals (+54p to 1846p), Capita (+10.4p to 500.5p), BT (+7.5p to 374.5p), Smurfit Kappa Group (+30p to 1,894p) and Unilever (+47p to 3,199p).
The biggest fallers in the FTSE 100 Index were Ashtead Group (-40p to 1,571p), Barclays (-4.2p to 224p), Antofagasta (-10.5p to 659.5p), AstraZeneca (-67.5p to 4,333.5p) and Standard Chartered (-10.5p to 674.5p).
In afternoon trading the biggest risers in the FTSE 250 Index were Drax Group (+24.5p to 348.5p), NMC Health (+66p to 1515p), Berendsen (+22p to 837p), TalkTalk (+4.3p to 169.3p) and Centamin (+2.9p to 119.3p).
The biggest fallers in the FTSE 250 Index were Evraz (-31.4p to 231.7p), PayPoint (-41.5p to 903.5p), Hastings Group (-6.9p to 224.1p), Kaz Minerals (-10.6p to 358.9p) and Ferrexpo (-3.7p to 135.1p).