Rental properties across the capital are empty for an average of 24 days.
The lender has also upped the maximum loan size on 80% LTV products to £2m, on 85% LTV offerings to £1.5m and on 90% LTV deals to £1m.
There were 29,490 of these mortgages recorded.
The RLA cited the 3% stamp duty levy on extra housing added in 2016 as slowing down investment in new rented property.
The growing number of landlords opting for shorter-term rates has been fuelled by the shorter early repayment charge periods.
Over a quarter (27%) of landlords experienced an increase in tenant demand during the final quarter of 2019.
In 2019 there were 2.66 million landlords in Great Britain, 8% fewer than the 2017 peak.
The ‘Boris bounce’ combined with the traditional New Year upsurge in activity combined to create a positive January.
Some rates have fallen by nearly £50 per month.
Just 18 individual landlords and property agents and five companies are registered on the database of rogue landlords.