FTSE 250 midcap stocks open lower by almost 1% after a profit warning from economic bellwether Clarkson (CKN).

The shipping services outfit trades 20% lower at £17.53 as it reports its Clarksea Index, which measures global shipping activity, was 30% lower in the first half of 2016 compared to a year earlier.

As a result, profit at Clarkson will be 'materially lower' in its 2016 financial year, management says.

Blue chip stocks open flat – the FTSE 100 trades at 6,585 – as it eyes a fifth straight day of gains in a post-Brexit bounce.

Sterling also opens after the weekend roughly flat against the dollar and euro, buying $1.3283 and €1.1936.

Firmer commodity prices are driving the early moves at the larger end of the market, with Mexico-based gold and silver miner Fresnillo (FRES) the biggest FTSE 100 gainer, up 7.5% to £17.92.

Silver prices surged 4.5% to $20.46 overnight, with gold and copper also gaining more than 1%.

Alcoholic drinks giant Diageo's (DGE) post-Brexit rally continues, shares in the Johnnie Walker whisky-to-Smirnoff vodka producer improving 1.5p to £21.09.

Already rewarded by the market for its favourable foreign exchange exposure, Berenberg, a buyer with a £23.50 price target, argues Diageo's next numbers should show an improvement in trading, 'allowing it to re-rate towards spirits peers'.

Mid cap and small cap movers

Coal miner and support services provider Hargreaves Services (HSP:AIM) reports in-line trading ahead of a full-year announcement on 9 August, helping shares 3% higher to 187p.

It also flags a Brexit-related contract delay, as a £7 million earthworks project at a major UK port is postponed.

'We currently consider the risk of a downturn in private sector activity as against the potential upside from Government-sponsored public sector works to reflate the economy to be relatively finely balanced,' says chief executive Gordon Banham.

Leicestershire-based British premium lifestyle brand Joules (JOUL:AIM) firms 1.75% to 174p following a positive write-up in the The Mail on Sunday.

A decent production update sends Kazakhstan-based copper producer Central Asia Metals (CAML:AIM) up 1% to 153.63p. An expansion plan is running on schedule and under budget.

ECR Minerals (ECR:AIM) dives 25% to 0.01p in line with the level of discount at which new shares will be issued. The miner has raised £350,000 through the equity issuance to repay a loan facility.

Drug developer C4X Discovery (C4XD:AIM)  rises 3.5% to 101.5p after discovering several potential leads to develop new Rheumatoid Arthritis and Parkinson's disease drugs. These are a result of its genetic analysis technology.

Cancer diagnostic developer Oncimmune (ONC:AIM) nudges 1.7% higher to 120p after signing two research agreements. Aarhus University Hospital and private company Egybiotech will provide blood samples to help prove that its technology can detect liver and ovarian cancers.

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Issue Date: 04 Jul 2016