London’s main share index closed marginally lower on Friday, with Royal Mail and house builders seeing some of the biggest falls, but the pound strengthened.The FTSE 100 ended the day at 7,378, which was 35 points or 0.47% lower than its previous close.Barratt Developments was the biggest faller on the FTSE, down 2.5%. Persimmon’s shares were down 1.5%.Royal Mail shares were down 2.4% after it put forward a new pensions proposal.The pension plan will give postal workers a choice between a defined benefit or contribution pension scheme.Separately, analysts at Liberum reiterated their “sell” rating on Royal Mail and cut their target price for the shares to 385p.Shares in drugs giant AstraZeneca slid for a second day following a report that its chief executive, Pascal Soriot, is to leave the company to join Israel-based Teva Pharmaceutical Industries.Shares in AstraZeneca fell nearly 3.5% on Thursday and slipped a further 0.29% on Friday. In the FTSE 250, shares in building and services firm Carillion initially rose 8% after it said it had appointed HSBC as joint financial adviser and corporate broker to help it carry out a review of the business. But it lost some of those gains to end the day just 1.26% higher. Carillion’s shares plunged earlier this week after it said on Monday that its annual sales would fall short of expectations, it needed to strengthen its finances and that its chief executive was to leave.Friday’s small rebound took Carillion’s share price to about 56.15p, but it remains well below the 191p level it was trading at last week.On the currency markets, the pound rose 1.04% against the dollar to $1.3074 and edged up 0.51% against the euro to 1.14120 euros.