Long-term investment opportunities attract Panmure Gordon to real estate group British Land (BL), as the broker expects a potential acquisition to expand the group's strong portfolio of retail properties.Weekend press reports suggest that BL has agreed heads of terms to acquire the Drake Circus shopping centre in Plymouth for £235m, which would provide over 500,000 sq ft of retail space and would "sit well among BL's assets", says the broker.Through its strong and diverse group of long-lease tenants, BL "enjoys high levels of occupancy and, importantly, it has few near-term breaks/expiries, and therefore a stable income stream", the broker adds.With the shares offering the best dividend yield in the broker's "coverage universe", the stock is seen as an attractive, long-term investment proposition. A 'buy' is retained with a target price of 548p.