Despite the bullish reports published this week about how the buy to let market is going from strength to strength, some London landlords are reportedly sweating out a short period of under-demand that has left some agents with dozens of empty rental properties on their books.

While agents reported a brisk start to the year, we have heard anecdotal evidence from a number of sources that the second half of January was drastically slower. One Wimbledon lettings office reportedly had 52 two-bedroom flats on its books this time last week, compared to a historical average of 10 or 15 such properties.

One letting agent from the office, who did not want to be named for fear of putting off cautious landlords, said that all their offices across London were experiencing similar problems. He said that some 2-bedroom properties had been on their books for between 8 and 10 weeks, which is almost unheard of for what is normally the most popular type of rental property in the capital.

One of the factors seems to be the continued low level of interest rates, which have led to an increase in the number of first time buyers among certain groups of tenants. Two bedroom flats are particularly popular with young professionals - just the sort who may consider buying in the current low interest climate.

Many of those tenants who still feel that buying is beyond their reach are trying their arm at a spot of negotiating, having realised that some agents have so many properties on their books. Where this is the case, tenants are getting away with making offers on properties at significantly lower than the advertised rent, which has caused a temporary drop-off in rental values in some areas, with some properties reportedly being let out for as little as 90% of last years rent level.

Any landlords considering entering the market for the first time would be well advised to do some additional research into the current state of their local market and make sure that they are not buying in an area that is currently oversupplied.

Any landlords already in the market should be prepared for longer than average void periods in the short term, and any who are forced to take lower rental values than they had anticipated would be well advised to ensure that tenancy agreements include a six month break clause. Provided that the contract allows it, this would then allow them to renegotiate the rent in August or September - traditionally one of the busiest times of the year for tenants.