Tesla Inc.'s long-term top external investor, U.K. fund manager Baillie Gifford & Co., said Wednesday that its stake in the electric-vehicle maker dropped to below 5% at the end of August but it intends to remain a long-term shareholder. The Edinburgh-based investment company said the recent rise in Tesla's share price meant it needed to reduce its holding due to guidelines which restrict the weight of a single stock in client portfolios. "However, we intend to remain significant shareholders for many years ahead. We remain very optimistic about the future of the company," James Anderson, co-manager of Baillie Gifford's flagship Scottish Mortgage Investment Trust PLC, said. "Tesla no longer faces any difficulty in raising capital at scale from outside sources but should there be serious setbacks in the share price, we would welcome the opportunity to once again increase our shareholding," he said. A regulatory filing...