(Sharecast News) - London's FTSE 250 was 0.41% lower at 20,846.51 in afternoon trade on Monday, with Tullow Oil leading the index downward.
Shares in the oil and gas company tumbled by more than 60% as it announced the departure of its chief executive officer, scrapped its dividend and cut production guidance.

AJ Bell analyst Russ Mould said: "The news represents a continuation of the problems which have dogged the company ever since its share price peaked more than seven years ago. The company's skill-set was in exploration - it enjoyed notable discoveries in Ghana and Uganda in the mid-noughties - and it has clearly found the transition to being more of a producer and developer of hydrocarbons more difficult.

"The appetite for risk which served it well when exploring for oil and gas arguably left it in a perilous position when it had too much debt heading into the oil price crash in 2014. Despite efforts to reduce borrowings, this remains an issue for the company, with net debt totalling nearly $3bn."

The news also sent its contemporary, Premier Oil, into the red.

Aston Martin dropped back lower, having racked up strong gains at the tail end of last week after reports on Thursday claimed Canadian billionaire Lawrence Stroll - father of Formula 1 driver Lance Stroll - was preparing to bid for a major stake in the luxury car maker.

According to analysts at Deutsche Bank, Aston management present at the firm's official opening of its St Athan site, at the weekend, made no comments regarding those reports.

Up at the other end of the index, precious metals miner Centamin topped the risers as gold prices firmed up.

Engineering group Senior rallied as it confirmed it was considering a sale of its aerostructure unit after recent speculation.

Finally, Marks & Spencer was boosted by an upgrade to 'buy' at Goldman Sachs, with analysts hiking their third quarter growth estimates for the high-street stalwart's clothing and home divisions.

Market Movers

FTSE 250 (MCX) 20,846.51 -0.41%


FTSE 250 - Risers

Centamin (DI) (CEY) 126.60p 6.79%
Senior (SNR) 189.30p 6.35%
Kaz Minerals (KAZ) 497.60p 3.41%
Plus500 Ltd (DI) (PLUS) 845.20p 3.33%
Drax Group (DRX) 297.80p 2.97%
Energean Oil & Gas (ENOG) 935.00p 2.75%
Marks & Spencer Group (MKS) 206.60p 2.68%
OneSavings Bank (OSB) 408.40p 2.51%
Ferrexpo (FXPO) 143.85p 2.17%
Ultra Electronics Holdings (ULE) 2,066.00p 2.08%

FTSE 250 - Fallers

Tullow Oil (TLW) 48.30p -65.84%
Aston Martin Lagonda Global Holdings (AML) 584.60p -7.21%
Premier Oil (PMO) 90.04p -4.66%
Future (FUTR) 1,344.00p -3.72%
Sirius Minerals (SXX) 3.43p -3.60%
Playtech (PTEC) 374.90p -3.00%
PureTech Health (PRTC) 247.00p -2.76%
FirstGroup (FGP) 114.30p -2.31%
Homeserve (HSV) 1,219.00p -2.25%
Network International Holdings (NETW) 580.00p -2.19%